growth of aquatic vegetation. Larval
development is unusually slow. The larvae that
hatch in any one season do not ordinarily
complete their development until the following
spring. Although they may detach from their
host plants and move about, the larvae remain
below the water surface during the entire
larval period. The pupae also have breathing
tubes adapted for penetrating plant tissues, and
they too attach to plants from which they get
their air. The pupal state requires 5 to 6 days.
The adults emerge in late spring or early
summer. There appears to be only one
generation per year throughout most of the
range of this species. It is possible that a
smaller second brood may be produced in
Florida. Larvae have been found attached to a
number of different kinds of plants,
particularly pickerel weed, cattail, water
lettuce, arrowhead, aquatic sedges, and swamp
loosestrife.

The females bite during the daytime in
shady, humid places but are much more active
in the evening and early part of the night.
They readily enter houses and bite viciously.
These strong fliers are frequently taken in light
trap collections.

Mansonia titillans

This tropical species is fairly common in
Florida and has also been reported from south
Texas. It has been found in nature infected
with Venezuelan equine encephalitis virus. The
adults are severe biters and fairly important
pests in Florida. The eggs of Ma. titillans are
laid on the under surface of the leaves of
water lettuce. The larvae and pupae attach to
the roots of this plant, developing in the same
manner as described for Cg. perturbans. The
adults are frequently taken in light traps.

THE GENUS PSOROPHORA
Fifteen species of Psorophora are found in
the United States, ten of which are widely

41

distributed in the southern and eastern states.
Two species, Ps. columbiae and Ps. discolor,
probably were important vectors of
Venezuelan equine encephalitis virus during
the Texas outbreak in 1971 (Sudia and
Newhouse 1975). Many species of Psorophora
are fierce biters. The larval habitats of this
group are similar to those of the typical Aedes,
to which they are closely related. Females lay
eggs on the ground. These eggs can withstand
drying and lie dormant for months. They hatch
quickly upon being flooded and the larvae
develop rapidly.

Figure 28. Psorophora ciliata

Psorophora ciliata (Gallinipper)

This is a very large, yellowish-brown
mosquito with conspicuous scales on the hind
tibia (Fig. 28). It is commonly known as the
gallinipper. Because of its vicious bite and
large size, this is one of the most formidable
mosquitoes. Psorophora ciliata is widespread
through the eastern United States from Mexico
to Canada. It is locally abundant in the South
and the Midwest. When present in numbers, it
is a very annoying pest that attacks both by


Figure 21. Anopheles quadrimaculatus

meal and egg laying begins from 2 to 3 days
after the first blood meal. A single female may
deposit a total of over 3,000 eggs in as many
as 12 batches.

During the daytime adults remain inactive,
resting in cool, damp, dark shelters, such as
buildings, caves, and under bridges. Feeding
and other activity occurs almost entirely at
night. They enter houses and readily feed upon
humans but they feed more frequently on other
warm-blooded animals such as cows, horses,
mules, pigs, and chickens. Normally, most
adults fly not more than one-half mile from
their larval habitat and only a small percentage
fly farther than one mile. Anopheles
quadrimaculatus is not ordinarily taken in light
traps in great numbers. In the most southern
part of the country, An. quadrimaculatus
Production occurs continuously throughout the
year. Over most of its range, however, it
spends the winters as fertilized adult females
in caves, hollow trees, basements, and other
protected places. In all but the most northern
areas females may emerge from hibernation
and move about and take blood meals on warm

35

days during the winter. In the spring, the
females emerge, take a blood meal and deposit
their eggs. There may be as many as 9 or 10
generations each season. Populations often
reach a peak during July or August and
decline rapidly in September and October.
Hibernating females may survive from 4 to 5
months.

Anopheles walkeri

This species resembles An.
quadrimaculatus, though it is somewhat darker
and has narrow white rings on the palpi. It is
widely distributed in eastern United States,
extending from southern Canada southward to
Vera Cruz, Mexico, and as far west as
Minnesota, Nebraska, Kansas, and Texas.
Anopheles walkeri readily bites humans and is
a good laboratory vector of malaria. Its past
epidemiological importance in relation to
malaria is undetermined.

Anopheles walkeri larvae are often found in
sunny marshes, or along lake margins, among
thick growths of aquatic vegetation such as
cattails and sawgrass. It may also be found
along the grassy edges of slow-flowing swamp
Streams and in bordering pools. In the
northern states it produces a distinctive type of
egg known as the "winter egg" in which stage
it passes the winter. The adults often rest
during the day on the lower part of the stems
of sedges and grasses and other emergent
vegetation of their larval habitats. Anopheles
walkeri is frequently collected by the hundreds
or thousands in light traps.

THE GENUS CULEX

The genus Culex includes about 300
species, most of which occur in the tropical
and subtropical regions of the world. Some 29
species have been reported in the United States
although only 12 of these are at all common.
The group includes several important pest


the upper surface of its abdomen. It has a
broad band of white scales at the base of each
tarsal segment (Fig. 12). This floodwater
species is an important pest mosquito
throughout the western plains from Minnesota
west to Washington and south to Texas and
Mexico. Since World War Il it has become
prominent in the irrigated pastures of the
West, especially in the Central Valley of
California. The remarkable spread of this
species is indicated by the fact that it was not
known to be in California until 1937. It now
occurs over most of the state at the lower
elevations and is rapidly replacing Ae. dorsalis
in open sunlit pools of irrigation waste water
and other intermittent water.

Figure 12. Aedes nigromaculis

This species is extremely well adapted to
pasture irrigation. The eggs will hatch within
2 to 6 days after flooding. It is able to produce
a brood following each irrigation (usually at

26

intervals of 8 to 12 days) in the Central Valley
of California. Under favorable conditions, a
brood can be produced in 5 days, and as many
as 20 broods can occur in one year. The adult
is a very annoying pest of man and animals, it
attacks readily and inflicts a painful bite. The
viruses of WEE, CE and SLE are associated
with this species.

Aedes punctor (and related species)

This group of dark-legged Aedes includes
such species as Ae. abserratus, Ae. pullatus,
Ae. communis, Ae. hexodontus, and Ae.
cataphylla, They are important woodland pests
in the northeastern states and in the
mountainous regions of the West. The females
of these species are difficult to identify. The
group is well represented throughout the
northern United States, Canada, and Alaska.

All species of this group have a single
generation per year. The larvae develop in
temporary pools formed by melting snow and
along the grassy margins of lakes, ponds, and
streams. The flight range of adults is probably
less than a mile. Females often cause great an-
noyance in recreational areas near their larval
habitats.

Aedes sollicitans (Saltmarsh mosquito)

Aedes sollicitans, the most important of the
saltmarsh species (Fig. 13), can be recognized
by the golden color of the upper side of the
thorax and longitudinal stripe of white or
yellowish-white scales on the abdomen. The
proboscis and tarsi also have wide pale bands.

The eggs of this species are laid on the mud
or on plants in marshes where they remain
until flooded by high tides or rains. Larval
production generally occurs on the parts of the
marsh not covered by daily tides; usually pot
holes and depressions of various size are
utilized, but sometimes large numbers of
larvae are found over rather extensive level
areas.



day and by night. Psorophora ciliata is one of
the few species whose larvae feed on other
aquatic insects, including mosquito larvae.
These larvae are found in temporary pools,
often in association with Ps. columbiae and
Aedes vexans, upon which they feed. A fourth
instar larva of Ps. ciliata can consume three or
four other larvae in one day. Psorophora
ciliata larvae are easily recognized in the field
as they are two or more times as long as
larvae of most other species. They hang almost
straight down from the water surface. The
larval and pupal stages are short as is
characteristic of this genus of mosquitoes. The
eggs are laid on the surface of drying soil.
They hatch when flooded as do Ps. columbiae.
Overwintering takes place in the egg stage.

Psorophora columbiae (formerly Psorophora
confinnis) (Dark rice field mosquito)

This species is known as the glades
mosquito in Florida and the dark rice field
mosquito in Arkansas and adjacent rice-
producing areas. It is a medium to large dark
species and has a narrow ring of white-scales
near the tip of each femur (Fig. 29).
Psorophora columbiae is the most widespread
and important species of Psorophora in the
United States. It occurs throughout the
southern United States, extending westward to
southern California and northward to Neb-
raska, lowa, New York, and Massachusetts. It
reaches its greatest abundance in the Florida
Everglades and in the rice fields of Texas,
Arkansas, and Mississippi. The females are
fierce biters, attacking anytime during the day
or night. When present in great numbers they
occasionally kill livestock and make it almost
unbearable for people to remain outdoors. This
species was incriminated in the transmission of
Venezuelan equine encephalitis virus during
the epidemic in Texas in 1971 (Sudia and
Newhouse 1975). Other viruses isolated from
the species include WEE and CE.

42

Figure 29. Psorophora columbiae

Psorophora columbiae larvae develop in
temporary rain pools, irrigation waters, and
seepage pools. Eggs are not laid on water
surfaces but on ground that is subject to
flooding from rainfall, overflow, or irrigation.
Soil with low, rank vegetation seems to be
ideal for egg deposition. Drained rice fields
are one of the preferred sites for egg laying. If
eggs remain on the surface of the soil for 2 or
3 weeks or longer, and are then flooded,
hatching can begin within a few minutes. This
species overwinters in the egg stage. During
the midsummer in Arkansas, the larval stages
can be completed in as few as 4 days. The
average time at a mean temperature of 79° F
is slightly over 5 days. The pupal stage lasts 1
or 2 days. The number of generations per
season is from one to many, depending on
how often suitable hatching conditions occur.
Areas which dry up and are then flooded a few
days later can produce a brood with each
flooding. Such conditions are provided with
certain types of irrigation, particularly wet rice
culture. Many adults live only a week or two:

Be RE

ste


OTHER MOSQUITOES

Five other genera of mosquitoes occur in
the United States. Four species of Uranotaenia
larvae are found in ground pools, the grassy
margins of lakes, and occasionally in tree
holes and pot holes. Uranotaenia sapphirina is
atiny species with brilliant iridescent scales on
some wing veins and the thorax. It is taken
readily in light traps. Four species of
Wyeomyia larvae develop in small collections
of water in the leaves of pitcher plants and
bromeliads, in other living or dead plants, and
in tree holes. Deinocerites cancer, De. math-
esoni, and De. pseudes comprise an interesting
genus of mosquitoes whose larvae are found in
salt water in crab holes in southern Florida

and Texas. Orthopodomyia signifera and Or.
alba are highly ornamented species that differ
chiefly in their larval stages. Their larvae
develop in water in tree holes and in water in
leaf bases of bromeliads. Orthopodomyia
sometimes are collected in large numbers in
artificial containers, such as old refrigerators,
when abundant organic matter is present. They
often share the containers with Culex restuans,
Cx. pipiens quinquefasciatus, and Aedes
triseriatus. The two Toxorhynchites
subspecies, rutilus and septentrionalis, are
large, brilliantly colored, nonbloodsucking
mosquitoes. The huge, clumsy larvae prey
upon other mosquito larvae in tires, tree
holes,bromeliads, and other water-holding
containers.

MOSQUITO SURVEYS

INTRODUCTION

Surveys are essential for the planning,
operation, and evaluation of any effective
mosquito-control program, whether for the
prevention of mosquito-borne diseases or the
lowering of populations of these biting insects
to a level permitting normal activities without
undue discomfort.

Two types of surveys are widely used:

1. The original basic survey determines
the species of mosquitoes, and their
sources, locations, densities, and flight
ranges. It can also include information
on life cycles, feeding preferences,
larval habitats, adult resting places,
transmission of human and animal dis-
eases, susceptibility to insecticides,
recommendations for a control
program, and the setting up of
immediate aims and _ long-term
objectives

2. The operational survey or
surveillance is a continuing evaluation,
which is extremely valuable in the
daily operation of a mosquito-control
program. It furnishes information on
the effectiveness of control operations
and data for comparison throughout a
season or from year to year.

Such surveys do not determine the absolute
population of mosquitoes as is done in the
human population census. Rather, an index of
population is obtained to show relative
fluctuations in mosquito abundance throughout
the period of the survey or in different areas in
the control zone.

MOSQUITO CONTROL MAPS

Reasonably accurate and comprehensive
maps are essential in planning a mosquito
contro! operation, in field survey and control
operations, in program evaluation, and in


Culex territans

Culex territans is widely distributed in the
United States, having been teported from
nearly every state. The larvae are found in
ponds and marshes that are well supplied with
aquatic vegetation, preferably in rather cool
waters. The adults apparently do not bite man.

THE GENUS CULISETA

Members of this genus are somewhat
similar in appearance and habits to Culex.
There are 8 species in the United States of
which 5 are fairly widespread. They are
relatively unimportant as pests. Two species
have been found naturally infected with
encephalitis virus but their relation to the
epidemiology of these diseases is not known.

Culiseta incidens

This is the most common culicine mosquito
with spotted wings in the United States. It is
Principally western in distribution and is
reported from Texas, Oklahoma, Nebraska,
and all states in the west. In some areas it is a
troublesome pest while in others it seems timid
about biting man. It is reported as feeding
more frequently on domestic animals. Culiseta
incidens larvae are found in a wide variety of
habitats, from the brackish water pools on the
Pacific Coast to spring water and snow pools
in the mountains. It has also been taken in
reservoirs, ornamental ponds, hoof prints, rain
barrels, and discarded automobile tires.

Culiseta inornata

This is a large, grayish-brown mosquito
with broad, pale-scaled wings (Fig. 25). It has
been reported from almost all the states except
in upper New England. In the northern and
western states it breeds throughout the spring
and summer; in the South it is more common
during the winter. This mosquito does not
usually attack man, but it does feed on

39

domestic animals and is sometimes a
considerable annoyance to livestock. Culiseta
inornata has been found naturally infected with
western equine encephalitis virus and
Jamestown Canyon virus. In laboratory
experiments it has been shown capable of
transmitting WEE virus. However, since it
seldom feeds on humans, it is unlikely to be
an important vector of WEE to humans.

Larvae of Cs. inornata are frequently found
in cold water. The hibernating females come
out during warm spells of the winter and early
spring even while snow is still on the ground.
They are sometimes referred to locally as
snow mosquitoes.

Figure 25. Culiseta inornata

Culiseta melanura (Blacktailed mosquito)
Culiseta melanura (Fig. 26) is a small dark
species that resembles members of the Culex
group more closely than do other species of
Culiseta. It occurs throughout most of the
eastern United States from the Gulf States to


GENUS ANOPHELES

Anopheline mosquitoes are distributed
throughout the United States. One or more
species is present in every state except Hawaii.
Most anophelines have spotted wings while
most culicines have no wing spots. Female
anophelines have the palpi about as long as the
proboscis, whereas female culicines have the
palpi much shorter than the proboscis.
Anophelines rest with the head, thorax, and
abdomen all in a straight line, held at an angle
of 40 to 90° to the surface on which they are
sitting. Culicines usually rest with the thorax
and abdomen somewhat parallel to the surface
on which they are sitting (Fig. 4).

The eggs of anophelines are always laid
singly on the water surface and are supported
by lateral floats. The female lays her eggs in
batches of 100 or more. Each female can lay
several such batches in her lifetime--a total of
400 to 500 eggs or more. The eggs hatch in
two to six days. Larval production is
continuous during the warm seasons of the
year.

Anopheline larvae are found in many
different types of water, but mainly in
permanent bodies of fresh water. Larvae of
two species, Anopheles atropos and An.
bradleyi are found in salt or brackish waters.
Larvae of all other anophelines in this country
develop in fresh water. The larval stages last
from 6 to 7 days to several weeks, depending
upon the species and environmental conditions,
especially water temperature. The larvae feed
just beneath the water surface where they
ingest microscopic animal and plant life.

Most anophelines favor water that contains
aquatic plants, and larvae are often abundant
where aquatic plants provide protection from
fish and other predators. Most adult
anophelines are active at night. They spend the
daytime hours resting in dark, damp shelters.
They are most active just after dark and again

31

just before daylight. The flight range varies
from less than one mile to several miles. Most
anophelines need a blood meal before they can
produce fertile eggs. The species in the United
States feed more frequently on the blood of
domestic animals than on man. The winter is
usually passed as hibernating, fertilized
females. Anopheles walkeri overwinters in the
egg stage. Anophelines were formerly highly
important as malaria vectors in the United
States. Currently, however, malaria
transmission in this country is a rarity,
although anopheline vector populations still
exist in many areas. Anophelines have been
found infected with encephalitis viruses and
might have a role in their transmission.

Anopheles albimanus

This species is the major vector of malaria
in the Caribbean Region and in Central
America, but has been found only in southern
Texas and the Florida Keys in the United
States. It is the only anopheline in the
continental United States with a broad white
band on the hind tarsus.

Anopheles crucians

This anopheline has areas of pale and dark
scales on the wings and three prominent dark
spots on the last wing vein. The palpi are
banded with white (Fig. 18). It has not been
considered an important vector of malaria.
However, it is susceptible to infection in the
laboratory and may have been the vector of a
case of malaria contracted in Georgia in 1968.
It bites humans readily but is not ordinarily
significant as a pest. It occurs throughout the
southeastern United States and northward
along the coastal plain to Massachusetts. It is
most abundant on the Atlantic and Gulf
Coastal Plains.

Anopheles crucians larvae are often found
in the acid water typical of cypress swamps
and ponds in coastal Florida and Georgia.


Adults are often very abundant following
spring floods. The females are ferocious biters
during the evening, and also during the day in
in cloudy or shaded situations. The flight
range is extensive, possibly up to 25 or 30
miles. They may live as long as 3 months.

Aedes "stimulans” Group

This group includes four common and
rather widely distributed woodland species:
Ae. stimulans, Ae. excrucians, Ae. fitchii, and
Ae. increpitus. Their habits are generally
similar and the adult females are difficult to
separate. They occur throughout most of the
northern states from New England to the
Pacific Coast, although Ae.  increpitus
apparently does not occur east of the Rocky
Mountains. These species are among the most
abundant and annoying of the woodland mos-
quitoes in many of the northern states. They
bite readily in the daytime. There is only one
generation a year but the adults may live most
of the summer. The winter is passed in the egg
stage, hatching with the melting of the ice and
snow in early spring.

Aedes taeniorhynchus
mosquito)

This species, known as the black saltmarsh
mosquito, has cross bands of white scales on
the upper side of the abdomen, a white band
on the proboscis, and white bands on the tarsi
(Fig. 14). It occurs on the coastal plain from
Massachusetts to Texas and on the Pacific
Coast in southern California. It has also been
reported from certain inland areas around salt
pools in oil fields. It is the most abundant and
troublesome salt-marsh species along the south
Florida coasts and can be a severe pest as far
north as New Jersey. It has been incriminated
as a vector of dog heartworm.

Larval habitats are similar to those of Ae.
sollicitans, but larvae are also found in fresh
water pools near the salt marshes. The adults

(Black — saltmarsh

28

Figure 14. Aedes taeniorhynchus

are strong fliers and fierce biters, being active
principally at night. They may be very
annoying in the shade during the day, but are
less likely than Ae. sollicitans to attack in
bright sunlight. According to Elmore and
Schoof (1963), 75 percent of the females in
one release study were recovered within 4
miles of the release point, but some females
were collected as far away as 18 miles.

Aedes triseriatus (Eastern treehole mosquito)

This tree-hole mosquito is blue-black and
has silvery-white scales on the sides of its
scutum (Fig. 15). It occurs throughout the
eastern United States, the larvae developing
principally in tree holes, old tires, tin cans,
barrels, and other artificial containers. Larval
development appears to be rather slow; nearly
a month is required to reach maturity. Adults
are fierce daytime biters in or near infested
woods, and are also annoying around



Figure 13. Aedes sollicitans

After the eggs have been dry for a week or
two, they hatch within a few minutes if
covered with water. The development of the
larvae and pupae to the adult stage requires 7
to 10 days during warm weather. Several
generations are produced each year in the
northern states. In South Florida breeding is
continuous throughout the year.

The adults of Ae. sollicitans are strong
fliers that often migrate in large swarms from
the marshes to cities and towns many miles
away. They often fly 5 to 10 miles and can
travel 40 miles or more. The migratory flights
begin just before dark and frequently consist
of tremendous numbers of mosquitoes. In the
daytime they rest on vegetation, and will
Teadily attack anyone who disturbs them, even
in full sunlight. They are fierce biters and
have been a very severe deterrent to the
development of some of the coastal resort
areas. Large numbers of females and males
are often collected in light traps, but the adults

27

do not often invade houses.

This mosquito species is considered to be an
important accessory vector responsible for the
transmission of Eastern equine encephalitis
from birds to humans and horses.

Aedes spencerii

This species, along with its close relative
Ae. idahoensis, is an important pest mosquito
of the prairie regions of Minnesota, North
Dakota, and Montana, extending northward
into Canada and southward to Illinois, Iowa,
Nebraska, and Utah. The females are fierce
biters, attacking during the day, even in bright
sunlight. They are serious pests of humans and
livestock. They often migrate into cities and
towns, but their flight range has not been
determined. There is probably only one
generation a year. The larvae are found in
surface pools filled by melting snow or spring
rains.

Aedes sticticus (Floodwater mosquito)

Aedes sticticus is a medium-sized species.
The scutum is striped with dark-brown scales
and the legs are speckled with white scales but
are not banded. It is a floodwater species that
occurs throughout most of the United States. It
is an important pest mosquito in such widely
separated areas as central New York and the
Columbia River Valley of Washington and
Oregon.

Aedes sticticus usually has only one brood
annually. The eggs are laid on the ground
particularly in the valleys of rivers and smaller
streams. A loam soil with either dead or live
vegetation or both, is preferred to bare areas
exposed to the sun and wind. Eggs do not
hatch until the spring or summer following the
season during which they were deposited. If
flooding does not occur eggs will survive 2 or
3 years. Larval development requires 10 days
to 3 weeks depending upon temperature.


Figure 26. Culiseta melanura

Canada. The larvae develop in water beneath
stumps and roots of trees in wooded swamps.
Adults have been taken in considerable
numbers in light traps and to a lesser extent in
daytime resting stations. This mosquito has
often been found naturally infected with the
viruses of Eastern equine, Highlands J and
California encephalitis. Culiseta melanura is
considered the primary vector of EEE virus
from bird to bird. Since it rarely bites man it
is not the vector of EEE virus to humans
(Chamberlain 1987).

THE GENERA MANSONIA AND
COQUILLETTIDIA
These closely related genera include three
species in the United States, one of which is
widespread and common. They are vicious
biters in many areas. They lay their eggs in
rafts on marshes or lakes. After hatching, the

40

larvae descend below the surface of the water
and insert their air tubes into the stems or
roots of aquatic plants. They remain below the
water surface throughout the larval and pupal
stages and obtain air from the plants. Because
of this unique habit, these larvae cannot be
controlled by the use of ordinary surface
larvicides.

Coquillettidia pertubans (formerly Mansonia
perturbans) (Irritating mosquito)

This is a rather large, speckled, brown and
pale mosquito (Fig. 27). It has characteristic
pale bands at about the outer third of both the
hind femur and the hind tibia. This species is
found in the southern and eastern states from
the Gulf Coast to Canada. It is also known
from some of the Great Plains and Rocky
Mountain states and from the Pacific Coast
states. This species has been found naturally
infected with the virus of eastern equine
encephalitis in many states from Florida to
New York. It may be a primary vector in
many inland areas.

ont ae

Ree

“N
\.
-~ ~N

ae = ~
= ~N
a ~—

Figure 27. Coquillettidia perturbans

Coquillettidia perturbans larvae are found in
marshes, ponds, and takes that have a thick



Figure 16. Aedes sierrensis

areas. It has been reported from every state,
and is a major pest in most of the northern
states from New England to the Pacific Coast.
It is less abundant in the extreme South. This
species has been found to be naturally or

experimentally infected with several
arboviruses including SLE, EEE, WEE and
LAC.

Aedes vexans larvae are found in rain pools,
floodwaters, roadside puddles, and practically
all temporary bodies of fresh water. Eggs are
laid on the ground, hatching when flooded. In
receding waters larvae may frequently be
concentrated so that 500 or more are found to
each pint of water. Development of the aquatic
stages requires 10 to 21 days, depending on
temperature. They are single-brooded in some
areas in the western states where flooding
occurs only in the spring. In most of the Ae.
vexans range there are several generations per
year.

Adults migrate long distances from their

30

Figure 17. Aedes vexans

breeding places 5 to 10 miles being rather
common. The adults are vicious biters and are
especially annoying at dusk and after dark.
Studies in Oregon have shown that the adults
live for nearly 2 months. They are attracted to
light, and both males and females are
frequently taken in light trap collections. They
rest during the day in grass and other
vegetation, and only rarely are found in
shelters of the type used for evaluation of
anopheline populations. Clarke and Wray
(1969) published an important article
indicating that Ae. vexans migrated several
miles into cities in Illinois about 15 days after
flooding by rain of an inch or more in a 24-
hour period. Their studies on light trap
collections, temperature, and rainfall as they
relate to fogging for adult mosquito control
contain important information for operational
personnel.



NOTES ON IMPORTANT SPECIES OF MOSQUITOES

THE GENUS AEDES

The genus Aedes, contains more than 500
species distributed from the polar regions to
the tropics. Almost one-half of all North
American mosquitoes belong to this genus,
which includes many of the major pest species
as well as important disease vectors. There are
some 70 species of Aedes known from the
United States of which about 40 may be rather
common, at least in certain regions. In general
the Aedes mosquitoes assume greater
importance as one goes from the tropics
northward. In the northern United States, as
well as in Canada and Alaska, many species of
Aedes occur and are often present in
astronomical numbers.

Species of Aedes characteristically lay their
eggs either singly on the ground, on the
waterline, or slightly above the waterline in
tree holes or containers. These eggs hatch
after flooding and in some species they are
able to survive long periods of drying. Many
of the northern species have only one brood a
year. Their eggs do not hatch until they have
been subjected to periods of drying or cold.
Other species are intermittent breeders and
have several generations per year depending
on rainfall or irrigation practices. Aedes
species occurring in regions with cold winters
pass the winter in the egg stage.

Larval habitats of Aedes are extremely
variable. In general, they are found in
temporary pools formed by rains, melting
snow, or overflows. Some species occur in
coastal salt marshes that are flooded at
intervals by unusually high tides. Others have
become adapted to irrigation practices. A few
species occur in tree holes, rock pools, and
artificial containers.

Practically all species of Aedes are blood
sucking. Many species are vicious biters of

22

great economic importance. Their biting habits
vary but they most frequently attack during
evening hours. Some species, however, bite
only during the day, and others bite either by
day or by night. Flight ranges are extremely
variable, being rather short for domestic and
woodiand species, and extremely long for
many floodwater and salt-marsh species.

Aedes aegypti (Yellow fever mosquito)

The yellow fever mosquito is a small dark
species that can be recognized by the lyre-
shaped silver-white lines on the thorax and the
white bands on the tarsal segments. It is the
vector of urban yellow fever and dengue, and
a pest of some significance when it occurs in
large numbers (Fig. 8).

Ae. aegypti was originally a tropical

Figure 8. Aedes aegypti

species, thought to have been introduced into
the Western World from Africa. Its current
distribution in the United States includes the
southeastern and southern states extending



generations are greatly reduced in Tange and
size by the recession of waters, except where
irrigation waters maintain their habitats. In late
fall at the end of the dry season, females
migrate long distances, sometimes 10 to 12
miles, finding shelter in outbuildings, homes
and cellars. During the winter season they are
in a state of semi-hibernation from which they
emerge on warm days and nights for feeding.
This winter feeding is seldom to repletion and
usually does not result in the development of
eggs.

Anopheles hermsi

Adults of Anopheles hermsi closely
resemble those of Anopheles Sreeborni_ as
described by Barr and Guptavanij (1988).
Studies by Fritz, et al. (1991) indicate that at
Present there are no reliable anatomical
characters that distinguish eggs, larvae, adults,
or X-chromosome of An. hermsi from those of
An. freeborni. These authors wrote “Crossing
studies or examination of rDNA restriction
enzyme profiles, are presently the only means
of identifying An. hermsi." Anopheles hermsi
occurs in California south of the Tehachapi
and west of the Coast Range as far north as
San Mateo county. An. freeborni has a wide
distribution in the western third of the United
States. Anopheles hermsi was probably the
vector of malaria from Mexican immigrant
agricultural workers to other migrants and a
few residents who had never been out of the
country in San Diego county, California in
1986 (27 cases) and in 1988 (30 cases).

Anopheles pseudopunctipennis

This species is similar in appearance to A.
Punctipennis except that the palpi are banded
with white (Fig. 19). It occurs in south central
United States, extending into Mexico, Central
and South America. Anopheles
pseudopunctipennis is considered an important
vector of malaria in foothill regions of Mexico

33

and parts of South America.

Figure 19. Anopheles pseudopunctipennis

Anopheles Pseudopunctipennis larvae are
found in pools in shallow or receding streams,
especially those in full sunlight containing
luxuriant growth of green algae. They also are
found in other ground pools, ponds, and
occasionally in artificial containers such as
fountains and tanks. They are often found in
water that is warm to the touch, much too
warm for other anophelines. Their flight range
is usually a mile or less.

Anopheles punctipennis

This mosquito has the wings conspicuously
marked with spots of pale and dark scales
(Fig. 20). The palpi are entirely dark. It
probably occurs in all of the contiguous states.
This species is not known to be a natural
vector of malaria although it may be infected
in the laboratory. It is a rather vicious biter
out-of-doors, but apparently does not enter
homes as readily as do An. quadrimaculatus
and An. freeborni.

Anopheles punctipennis larvae occur in a
wide variety of habitats. Larvae are often
found along with An. quadrimaculatus in


Figure 18. Anopheles crucians

Larvae are also found in many other habitats
such as lake margins, wheel ruts, and sluggish
streams. Adults are found in shelters of the
same type frequented by An. quadrimaculatus.
They are often taken in great numbers in light
traps. Their flight range may be somewhat
greater than one mile, especially in areas
where they are abundant. Two other species in
the An. crucians complex are An. bradleyi,
typically a salt-marsh breeder, and An.
georgianus, whose larvae are found in fresh
water seepage.

Anopheles franciscanus

Anopheles franciscanus is similar to An.
pseudopunctipennis in appearance and habits.
It occurs along the Pacific Coast from southern
Oregon into Mexico and eastward into
Nevada, Arizona, and New Mexico. It is often
present in great numbers in certain localities
but is not believed to have been an important
malaria vector. Anopheles franciscanus is
often found at the mouths of rivers entering
the Pacific and their larvae occur in abundance
in the shallow pools of sandy arroyos. Their

32

larval habitats are similar to those of An.
pseudopunctipennis.

Anopheles freeborni

This species is similar in appearance to An.
quadrimaculatus, and was the most important
vector of malaria in the western United States.
It enters houses and animal shelters readily
and bites avidly at dusk and at dawn. This
species occurs over most of the area west of
the Continental Divide, from southern British
Columbia to Lower California. East of the
Divide it is found from eastern Montana to
western Texas and eastern New Mexico.

The aquatic stages of An. freeborni are
found in permanent or semipermanent waters
that are at least partially exposed to sunlight,
and contain vegetation or flotage. Clear, clean,
slightly alkaline water is preferred. Larvae are
also found in slightly brackish water near the
ocean or in desert pools. This species usually
avoids water polluted with sewage or other
organic materials. Habitats may be very
similar to those in which An. quadrimaculatus
is found, but it has for the most part adapted
itself to seepage areas, borrow pits, hoof
prints, improperly irrigated fields, and the
edges of streams or irrigation canals. Rice
fields are a particularly favored site for this
species. This mosquito is well adapted to the
semi-arid region in which it occurs. The
midseason flight range of An. freeborni
females is usually restricted to a one-mile
radius. In cases of very large populations in
rice fields, longer flights up to 2 1/2 miles
have been reported. Males, however, are
seldom found more than one-quarter mile from
their larval habitats.

In California, An. freeborni \eave their
hibernating places in February, take a blood
meal, and lay eggs for the first generation.
Because of the abundance of water areas at
this time of year, and the scarcity of
predators, large broods develop. Succeeding



Figure 15. Aedes triseriatus

dwellings where larval development occurs in
containers or tree holes. The flight range is
characteristically short. This species is an
important vector of LaCrosse encephalitis
virus and dog heartworm.

Aedes trivittatus

Aedes trivittatus is widely distributed in the
northern United States from Maine west to
Idaho. It has been collected as far south as
Georgia, Louisiana, and Arizona. It is a fierce
biter and an extremely annoying pest in some
of the northern states. The upper surface of
the thorax is marked with two conspicuous
whitish stripes. The larvae occur mostly in
floodwater pools and temporary rain pools.
The young larvae feed at the surface of the

29

water but the later instars spend most of their
time concealed in the vegetation at the bottom
of the pool. Perhaps it is for this reason that
Jarvae are seldom encountered even though
adults may be present in large numbers.
Emergence of adults begins about 8 days after
hatching. The adults rest on grasses and other
vegetation during the daytime. They will bite
when disturbed and are especially active in the
evening. They do not appear to migrate far.

Aedes "varipalpus" Group (Western treehole
mosquito)

Collectively, these western  tree-hole
mosquitoes are a group of small, dark species
with brilliant white bands at both ends of each
tarsal segment (Fig. 16). They occur in
western North America from Arizona to
British Columbia, and are important as pest
species in some parts of California. At
present, Aedes sierrensis is considered the
correct name for the species on the Pacific
Coast. Aedes varipalpus, Ae. deserticola, and
Ae. monticola occur in other parts of the
West. These species ordinarily breed in tree
holes, but may also occur in rain barrels that
contain a heavy sediment of decaying leaves.
The adults are often so small that they can
pass through ordinary window screens.
However, they seem to bite less readily
indoors than outdoors. Aedes sierrensis has
been shown to be an experimental vector of
WEE and vector of dog heartworm.

Aedes vexans (Inland floodwater mosquito)
Aedes vexans (Fig. 17), the inland
floodwater mosquito, is a medium-sized,
brown mosquito with narrow rings of white
scales on the hind tarsi and with a V-shaped
notch at the middle of each band of white
scales on the upper surface of the abdomen.
This is probably the most widespread species
of Aedes in the United States and the most
abundant and troublesome mosquito in many


rea

some live as long as a month or two. The
flight range is at least 10 miles.

Psorophora cyanescens

This metallic blue species has entirely dark
tarsi. It has been reported from ali the
southern states north to Illinois and Indiana. It
is abundant in Oklahoma and Arkansas, as
well as in certain areas of Alabama, Miss-
issippi, Louisiana, and Texas. It is a vicious
biter and attacks during either the day or
night. In Arkansas and Oklahoma, it has on
occasion become extremely numerous and
pestiferous after rains in July and August. It
breeds in temporary rain pools and its life
history is similar to that of Ps. columbiae. It
was a most annoying pest in the Rio Grande
Valley in Texas following the floods of 1967.

Ss
SS
7.

2s

Figure 30. Psorophora ferox

43

Psorophora _ ferox
mosquito)

This brilliant blue-purple mosquito is known
as the white-footed woods mosquito because
the last two segments of the hind tarsi are
entirely white (Fig. 30). It occurs in swampy
woodlands in most of the states from Texas to
Nebraska and eastward. It is a persistent and
painful biter that attacks readily during the
day. The larvae, which develop in temporary
Pools, are easily recognized by their antennae
which are longer than the head.

(White-footed woods

Psorophora signipennis

This is a common species in the central
United States from Montana and North Dakota
to Texas. It is very abundant in Oklahoma,
Nebraska, and Kansas. This species inflicts a
painful bite, but does not appear to be as
Severe a pest as the numbers taken in light
traps might indicate. Both LAC and WEE
viruses have been isolated from this species.
Psorophora signipennis is well adapted to
breeding in temporary ground pools in arid
regions. Its development from egg to adult can
be completed in 5 days under favorable
conditions.

Other Species of Psorophora

A number of other species of Psorophora
can be annoying at times, particularly in the
southern states, and one or more may be
important in disease transmission. These
include P. discolor, P. horrida, P. varipes, and
P. howardii. The latter is very similar to P.
ciliata in both larval and adult habits. The
other three species have breeding habits
similar to P. columbiae but are rarely as
abundant.


Aedes cantator (Brown saltmarsh mosquito)
The brown salt-marsh mosquito is a rather
large, brown species with indistinct white
bands on the abdomen and tarsi. It is
important along the North Atlantic Coast from
Maine to Virginia. Aedes cantator is an
abundant and severe pest in the coastal
marshes of Massachusetts, Rhode Island,
Connecticut, New York and New Jersey. Its
habits are generally similar to those of Ae.
sollicitans, though it is not as active during the
day and is primarily an evening mosquito.
Broods frequently migrate considerable
distances, invading shore towns and summer
resorts. It is often the dominant species of the
salt marshes early in the season but yields this
position to Ae. sollicitans later in the summer.

Aedes cinereus

This small brown species occurs sparsely
throughout most the United States. It is
occasionally important as a pest mosquito in
some of the northern states. The flight range
of Ae. cinereus seems to be limited and it is
usually found in the woods near larval
habitats. It is usually single brooded. The
larvae occur in shallow woodland pools and
along margins of large ponds.

Aedes dorsalis

This is a medium-sized mosquito that varies
in color from dark brown to a whitish straw
color. The upper surface of its abdomen is
marked with a longitudinal stripe of pale
scales. The hind tarsi have both ends of each
segment banded with pale scales (Fig. 11).
Aedes dorsalis is a severe pest of humans and
cattle throughout the arid and semi-arid
regions of the western United States and has
been shown to be a vector of Western equine
encephalitis. It occurs over most of the
country, but is rare and unimportant in the
eastern and southern states. Another western
species, Ae. melanimon is very similar to

25

Aedes dorsalis.

A typical floodwater species, the larvae
develop in the salt marshes of the Pacific
Coast and in irrigation and floodwaters of the
interior. They are particularly abundant in
irrigated pastures and in waste-water pools.
Several broods are produced each year in ir-
tigated areas, each flooding being followed by
a brood.

Figure 11. Aedes dorsalis

The females of Ae. dorsalis are vicious
biters that attack by day or night. They are
particularly active in the evening or on calm,
cloudy days. They are strong fliers and
occasionally migrate in large groups. They
are often found miles from their larval
habitats. The females, and at times the males,
are taken in great numbers in light traps.
Overwintering takes place in the egg stage.
Some eggs can remain viable for several
years.

Aedes nigromaculis
This medium-sized mosquito has a
longitudinal line of yellowish-white scales on


species and disease vectors

Culex mosquito larvae are found in quiet
of almost all types, from that in
artificial containers to large bodies of
permanent water. Water in which there is
considerable organic material, including
sewage, is often a favored larval habitat. The
eggs are deposited in rafts of 100 or more.
They remain afloat on the water surface until
hatching occurs some 2 or 3 days later. Larval
development continues throughout the warm
season with several generations a year in the
southern states. The adult females are
generally inactive during the day, biting at
night

waters

Culex erraticus, (and the
Melanoconion)

Culex erraticus, Cx. peccator, and Cx.
pilosus are rather small and dark species found
in the southeastern states. The females are
difficult to determine. Larvae of Culex
erraticus, the most common species of this
group, occur in grassy permanent pools and
ponds often in association with anophelines.
They have been reported in great numbers in
the rice fields of Arkansas. The adults are
persistent and painful biters, though they are
said to prefer the blood of fowls. They bite

principally in the evening.

subgenus

Culex nigripalpus

This is chiefly a tropical mosquito but
occurs as far north as Tennessee and North
Carolina. It is quite common in Florida where
it is an important pest species in flooded
fields. Larvae are also found in ditches and
grassy pools. Culex nigripalpus was the vector
of St. Louis encephalitis virus in the Tampa
Bay, Florida, outbreak in 1962 (Chamberlain,
1987), and in Florida in 1990

Culex stigmatosoma

‘This is a western species similar in

36

appearance to Cx. tarsalis, Larvae are found
in almost all types of ground pools and
artificial containers. In California tremendous
numbers of larvae have been reported in
oxidation ponds. Culex stigmatosoma rivais
Cx. tarsalis in abundance in the Pacific Coast
states, but apparently seldom bites humans. It
has been found infected with western equine
encephalitis virus.

Culex pipiens Complex (Northern and southern
house mosquitoes)

The northern and southern house
mosquitoes are closely related and difficult to
separate. They are brown mosquitoes of
medium size with cross bands of white scales
on the abdominal segments but without other
prominent markings. Culex pipiens pipiens, the
northern house mosquito, occurs throughout
northern United States and is found as far
south as Georgia and Oklahoma. Culex pipiens
quinquefasciatus, the southern house mosquito,
(Fig. 22) occurs in all southern states from
coast to coast and is found northward to
Nebraska, lowa, Illinois, and Ohio. One or
both of these mosquito species are found in
every state. In many published articles from
outside the United States, this mosquito is
referred to as Culex fatigans.

In the United States, members of the Culex
pipiens complex are important vectors in urban
epidemics of St. Louis encephalitis.

Culex pipiens pipiens and Cx. pipiens
quinquefasciatus develop prolifically in rain
barrels, tanks, tin cans, and practically all
types of artificial containers.

Other important sources of these mosquitoes
are storm-sewer catch basins, poorly drained
street gutters, polluted ground pools,
cesspools, open septic tanks, and effluent
drains from sewage disposal plants. Heavy
production is often found in water with high
organic content

House mosquitoes lay their eggs in clusters



eastern United States. It is especially common
along the Atlantic and Gulf Coasts. It bites
readily out-of-doors at night and is at times a
fairly important pest. Larvae are found in
grassy pools of both fresh and brackish water,
along lake margins, and in marshes, cattail
bogs, ponds, and ditches.

Culex tarsalis

Culex tarsalis mosquito (Fig. 24) is a
medium-sized, dark species with a broad,
white band at the middle of the proboscis and
white bands at each end of the tarsal segments.
It is an important pest species in some parts of
its range. It is most active soon after dusk and
may enter buildings in search of blood.

Culex tarsalis has been found naturally
infected with the virus of both St. Louis and
Western equine encephalitis and laboratory
experiments have also demonstrated its ability
to transmit both diseases. Culex tarsalis is
considered to be the most important vector of
encephalitis to man and horses in the western
states (Reeves 1990).

Culex tarsalis is widely distributed and
abundant west of the Mississippi River. It
occurs less commonly east to Ohio, Rhode
Island, Virginia, and Florida, and in
southwestern Canada and northern Mexico.

Larvae of this species develop in a wide
variety of aquatic situations. In the arid and
semi-arid regions, they utilize almost all types
of water and are most frequently found in
temporary to semipermanent bodies of water
associated with irrigation. These include
canals, ditches, borrow pits, impoundments,
ground pools, and hoof prints. Larvae develop
in effluent from cesspools and other waters
containing large quantities of organic material
from human wastes, and in artificial containers
of various types such as cans, Jars, barrels,
drinking troughs, ornamental ponds, and catch
basins. Females deposit egg rafts that contain
from 100 to 150 or more eggs each. The eggs

38

Figure 24. Culex tarsalis

usually hatch within 48 hours. The larval and
pupal stages develop rapidly. Larval
production continues from early spring until
late fall.

Adult females hibernate in the northern
areas of the United States. Adults are active
chiefly from dusk to dawn. During daylight
hours the adults remain quietly at rest in se-
cluded spots. They can frequently be found on
porches, on shaded sides of buildings, in
privies, or under bridges. The majority,
however, rest in grass and shrubs, in rodent
burrows, or along cut banks of streams. Tt has
a wide range of hosts, showing some
preference for birds, but also feeding on cows,
horses and humans. Dispersion studies have
shown that Cx. tarsalis will fly at least 11
miles, although the majority probably remain
within a mile of their breeding places. They
are taken in considerable numbers in light
traps and in traps using dry ice (carbon
dioxide) as the attractant (Sudia and
Chamberlain 1967).

—— ae Ce



The Asian tiger mosquito resembles the
yellow fever mosquito (Ae. aegypti) in having
bright silvery thoracic and abdominal markings
and white-banded legs. Ae. aegypti has a
characteristic silvery lyre-shaped marking on
the scutum whereas Ae. albopictus has a single
longitudinal silvery stripe in the middle of the
scutum hence its name (Fig. 9). The larvae of
both species, and the treehole mosquito (Ae.
triseriatus) are found in water-holding
containers, particularly used tires, but differ in
the shape of the comb scales and other
characters as discussed by Darsie (1986). The
biology of Ae. albopictus is described in detail
by Hawley (1988). The mean development
time from egg hatch to pupation takes 5 to 10
days at temperatures near 25° C (77 °F) but
may take longer at lower temperatures or with
suboptimal larval food. Adult females live
longer than males. Females live from 4 to 8
weeks in the laboratory but may survive up to
3-6 months, particularly if water, sugar from
flowers, or blood is available. In some parts
of southeastern United States Aedes albopictus
is replacing Aedes aegypti and is becoming
more abundant than Ae. aegypti.

Aedes atlanticus

These brownish mosquitoes with a white
stripe on the scutum (Fig. 10) can be separated
from Ae. tormentor only in the larval stage or
by the male genitalia. They are distributed
throughout the southeastern states. The species
is typically a "woodland" floodwater species
whose larvae are found in flooded woodland
bottoms or temporary grass pools in or near
woods.

Aedes canadensis (Woodland pool mosquito)

This dark mosquito has the tarsi with white
at both ends of the segments. It is widely
distributed in the United States and is
particularly common in the northern states. It
is often a serious pest in woodland situations

24

Figure 10. Aedes atlanticus

but rarely migrates far from its larval habitats.
The viruses of LaCrosse and Eastern Equine
encephalitis have been isolated from this
species. It has been incriminated in the trans-
mission of dog heartworm (Crans and
Feldlaufer 1974).

Aedes canadensis is one of the first
mosquitoes to appear in early spring. The
larvae live in woodland pools filled by melting
snow or by spring rains. This mosquito prefers
pools with a bottom of dead and decaying
jJeaves, although larvae are also found in road-
side puddles, sink holes, wooded swamps, and
isolated oxbows of small woodland streams.
There can be more than one generation per
year. The adults live for several months.
They usually occur from March until October,
although they become less abundant in late
summer and early fall.



northward to North Carolina, Tennessee and
Arkansas. It was formerly an abundant species
in most southern cities and extended northward
along the Atlantic Coast probably into New
England and in the Mississippi basin only as
far north as Illinois.

Aedes aegypti is semi-domesticated. Its
larval habitats are almost exclusively in
artificial containers in and around human
habitations. The eggs are laid singly on the
inside of containers at or above the waterline,
or less often on the water surface. They are
able to withstand drying for several months
and hatch quickly when containers are again
filled with water. Hatching can take place in
two or three days if temperatures are high.
Typical artificial containers are flower vases,
tin cans, jars, discarded automobile tires,
unused water closets, cisterns, rain barrels,
Sagging roof gutters and tree holes.

The larvae can complete their development
in 6 to 10 days under favorable conditions. In
cool weather development is longer. The pupal
period is about 2 days. The life cycle can be
completed in 10 days, or it may vary as long
as three weeks or more. This mosquito breeds
throughout the year in the tropics, where
generations succeed each other rapidly. In the
southern United States, the reproduction rate
is slower during the winter. The eggs
sometimes remain dormant for several weeks
or months. This species is very susceptible to
cold and usually does not survive the winter in
the northern United States.

The adults apparently prefer the blood of
man to that of other animals. Aedes aegypti
enter houses readily, even those that are well
screened. This mosquito bites Principally
during the moming and late afternoon. It
attacks quietly and prefers to bite about the
ankles, under coat sleeves, or at the back of
the neck. It often becomes a troublesome pest.
The adults live four months or More in the
laboratory. Their usual flight range is from

23

,

100 feet to 100 yards, but longer distances
have been recorded.

Aedes albopictus (Asian tiger mosquito)

The Asian tiger mosquito was introduced
many times into the United States, usually as
eggs or larvae in used tires from Asia. It
became established and was detected in
Houston, Texas in 1985 and has since spread
to 21 states and 257 counties. Known
infestations have been reported as far east as
Florida and Georgia, north to Maryland and
Delaware in the east and Chicago, Minnesota
and Nebraska in the west. Aedes albopictus
has been reported as a vector of dengue in
Hawaii, the Philippines, and Southeast Asia.
It is a competent vector of Dirofilaria immitis,
the heartworm of dog. It has been found
infected with the virus of eastern equine
encephalitis in Florida (Mitchell, et al., 1992).
Ae. albopictus strains established in the United
States are efficient vectors the viruses of
dengue and LaCrosse encephalitis in the
laboratory (Francy et al., 1990; Mitchell,
1991).

Figure 9. Aedes albopictus


Figure 20. Anopheles punctipennis

permanent pool situations, or in rain barrels,
hog wallows, grassy bogs, spring pools,
swamps, and along margins of streams. They
seem to prefer cool water and are the first
anophelines to appear in the spring. They are
the most abundant during the spring and fall in
the southern states but are found in more
uniform numbers throughout the summer in
the northern states.

Anopheles quadrimaculatus (Common malaria
mosquito)

This fairly large, dark brown mosquito has
four dark spots near the center of each wing.
The palpi and tarsi are entirely dark (Fig. 21).
This species was the most important vector of
malaria in the United States. It is the
anopheline most frequently found in houses
and is, with the possible exception of An.
freeborni, more likely to attack humans than
any other anopheline of the United States.
Anopheles quadrimaculatus has probably been
responsible for the transmission of almost all
human malaria that has occurred east of the
Rocky Mountains.

34

This species is distributed from the
southeastern United States northward to
southern Quebec and Ontario and westward to
the Dakotas, central Nebraska, Kansas,
Oklahoma, and Texas. It also occurs in
Eastern Mexico as far south as Vera Cruz. It
is most abundant in the South Atlantic and
Gulf Coastal Plains and the lower Mississippi
River Valley. It may also become abundant at
times in areas as far north as Minnesota,
Michigan, New York, and New England.

Anopheles quadrimaculatus larvae are found
chiefly in permanent fresh water pools, ponds,
and swamps which contain aquatic vegetation
or floating debris. It is most abundant in
shallow waters. In some areas it appears to
favor open sunlit waters while in others it is
found in densely shaded swamps. This species
shows a preference for clear, quiet waters
which are neutral to alkaline and does not
usually occur where the pH is lower than 6. It
seldom occurs in stagnant waters heavily
polluted with plant or animal matter. Some of
the common habitats are lime-sink ponds,
borrow pits, sloughs, bayous, sluggish streams
and shallow margins, and backwater areas of
reservoirs and lakes. Production is greatest in
waters with aquatic vegetation or flotage of
twigs, bark and leaves.

The most favorable temperature for the
development of An. quadrimaculatus is
between 85 and 90° F at which temperature
only about 8 to 14 days are required. The
larvae can withstand rather low temperatures,
but do not complete their development at tem-
peratures below 50 to 55° F and no
appreciable development takes place until the
water temperature reaches 65 to 70° F. Even
at these temperatures from 30 to 35 days may
be required for development of the aquatic
stages. The males emerge first,
remaining near the larval habitats. The females
mate soon after emergence, often during their
first day, either before or after the first blood



Figure 22. Culex pipiens quinquefasciatus

of 50 to 400. These clusters, known as egg
rafts (Fig. 4), float on the surface of the
water. The eggs hatch within a day or two in
warm weather. From 8 to 10 days are required
for completion of the larval and pupal stages.
In somewhat cooler weather of early spring or
late fall, these aquatic stages may require
weeks or more. Larval production continues
throughout the warmer months of the year.
Some strains can survive and produce fertile
eggs without a blood meal (autogeny).

House mosquitoes migrate only short
distances unless great numbers are produced.
Ordinarily, when adults are present, larvae
will be found nearby. These species are active
only at night and may be found resting during
the day in and around houses, chicken houses,
outbuildings, and various shelters near their
larval habitats. They are attracted to light
traps, but the numbers collected may not
represent an accurate index of their actual
abundance.

37

Culex restuans (White dotted mosquito)

This species is widely distributed east of the
Rocky Mountains from the Gulf of Mexico
into Canada. Some observers report that it is
often abundant and annoying in the eastern
states, while others say that it rarely bites
man. It is similar in appearance and habits to
Cx. pipiens although it is not usually as
important a pest and is more rural in its
occurrence. It is distinguished from Cx.
pipiens by the two silvery dots on the scutum
(Fig. 23) and by the pattern of bands on the
abdomen.

Figure 23. Culex restuans

Culex restuans larvae often are found in
rather foul water such as that containing
decaying grass or leaves. Favored larval
habitats are woodland pools, ditches, pools in
streams, rain barrels and tin cans. It appears
early in the season and continues development
throughout the summer.

Culex — salinarius saltmarsh
mosquito)

Culex salinarius occurs throughout most of

(Unbanded