Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1916-12-18
COMMON FLOWER FLIES
Beneficial Habits of Their Larvae

orono. Me-, Dec. 12.-(SpeciaD.- The
following was made public today by
Charles D. Woods, director or the
Maine agriculture experiment statlon
at the University of Maine:
In Bulletin 253 of the Maine Agr1cul-
tural Experiment Station by Professor
Metcalf of the Station Summer STAFF,
is discussed the above topic as follows:
By far the most important economic
bearing Of Syrphidae arises from tne
predaceous habit of the larvae OF many
common species. Of the prey affected
aphids compose probably ninety-nine
per cent.
With the vast majority of species
there is no close restriction to particu-
lar species of prey; although a rev
species such as Didea fasciata and
Pipiza pisticoides have been found
among only one or few species OF
aphids.
For the most part the service OF these
insects is in preventing the abnormal
increase of the various injurious spe-
cies of aphids rather than In extermln-
atinr the colonies in any particular
mace. although the latter result Is by
no means uncommon inelr Value ID
ordinarily due to their very UNIFORM
distribution and constant occurrence
rather than to tremendous NUMBERS al
any time or place. NeVertneless' AZ
s+ances of the occurrence OF enormous
numbers of them are not lacking. FER
HANG tho most notable OF such RECORDS
is that by w. G. Johnson regarding the
abundance of larvae during an OUT
break Of the pea-louse IN southern
MARYLAND in 1899. quote from Ml'
Johnson as follows:
"Thc real importance Of the syrphus-
A., Iarvae In the reduction of the spe-
clos fthe -louse) was shown beauu-
f,,1Jv in southern Maryland, where they
were so abundant the first and secono
weeks in June as to almost coihpie.els
destroy the lice" And quoting further
from his correspondent The insects
nice) started to disappear last week
and are now about all gone The
last few DAYS I packed. the separators
solved out about 25 bushels of green
worms Uarvae of Syrphidae. chiefly
Allograpta obliqua) which no DOUBT
proves that they destroyed the lice
Mr.. johnson states further that the
Svrhoid-f1ies did not save the crop
that wear but calls attention to their
nrobable value in relation to future
ravages of the pest. conservative
estimate shows that twenty-five BUSH
els of the larvae Of Allograpta obliqua
could scarcely represent less than B.
COZ, 900 individuals. Presenting that the
IoH- mr. al
average twenty aphids day (whlch
believe also to be conservative es-
timate) such q multitude OF larvae
would be responsible for the destruc-
ton Of over half a billion aphids.
Another example of the extermina-
ton Of aphid colonies by these preda-
ceous larvae is afforded by the attacks
Of Pipiza pisticoides on the Woolly APP
pie Aphis These aphids became evid-
ent as above-ground colonies on apple.
at Orono, about the first of August. AT
the same time several species OF Spy
phid larvae also made their appearance
among them. chiefly the larvae Of Pr
piza. Shortly the Woally Apple Aphis
began to disappear. The aphids be-
coming scarcer and scarcer and the
ident. until by early September
found myself with many larvae on
hand and almost no aphids anywhere
to be found as food for them. Doctor
Patch tells me she has found this
rather common experience; and that
year afteer year. the colonies of Woolly
Apple Aphis on apple have practically
disappeared in the presence Of these
predaceous larvae. by mid-September
The "reminiscences Of these enemies
Of aphids Is illustrated in a peculiar
way by the experience Of the Station
Entomologist, who for number Of
years has been studying the aphids of
the State. 1t is quite common expert
ence that aphid material mailed to her
for study has been absolutely consumed
en- route by Syrphid larvae, inadvert-
entity introduced into the package by
the correspondent.
Hardly a colony of aphids can be
found that is not being preyed upon
by from one to a half dozen species
and from one to a dozen of individuals.
They kill the individual aphids outright
but on account Of the rapid rate Of
reproduction of the latter the colony
usually exists for some time at least.
l have been interested in getting
some definite data as to the capacity
of these larvae for devourirg their
prey.
Specimens of Aphis brassicae offered
to four-day old unfasted larva Of
Surplus americanus were devcured at
the following rate: Four minutes AMI
f1C mi, 1
ute and 80 seconds; minutes and Is
seconds. minutes, 1 minute and As
seconds, and minute and 80
seconds: total of nine aph-
ids in seventeen and a half minutes
In this test the aphids were touched
to the mouth-parts of the larva as
rapidly as the previous skin was dis
carded. IT was thought that this rep