KARL V. KROMB Behavioral and LifeHistory Notes on Three

W Floridian Solitary Wasps

(Hymenoptera: Sphecidae) ,

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1970 NUMBER 46
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SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 46

Behavioral and LifeKarl V. Krombein TT . X T ,_ri1

History Notes on lhree

Floridian Solitary Wasps

(Hymenoptera: Sphecidae)

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

I97O
ABSTRACT

Krombein, Karl V. Behavioral and Life-History Notes on Three Floridian SolitaryWasps (Hymenoptera: Sphecidae). Smithsonian Contributions to Zoology, 46: 1 26,

1970.—A new trap to attract solitary twig-nesting wasps and bees was developed and

tested in Florida. It permits observation and photography of the nesting behavior

during nest construction and, subsequently, of the development of the progeny. Observations and photographs were made of the nesting behavior and subsequent development of three sphecid wasps, lsodontia (Murrayella) auripes (Fcrnald), Podium

rufipes (Fabricius), and Trypargilum collinum collinum (Smith).

Official publication date is handstamped in a limited number of initial copies and is recorded in

the Institution's annual report, Smithsonian Year.

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON : 1970

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price 40 cents (paper cover)
Karl v. Krombein Behavioral and LifeHistory Notes on Three

Floridian Solitary Wasps

(Hymenopter a: Sphecidae)

The need to perform field tests on a new type of trap

designed to attract solitary wood-nesting wasps and

bees provided the incentive for a period of study at

the Archbold Biological Station, Lake Placid, Florida,

7-26 April 1969. Normally during this season in southcentral Florida there is an abundance of many species

of both wood- and ground-nesting wasps and bees.

However, populations were abnormally low during my

stay, perhaps because the unusually cool wet winter

of 1968-69 resulted either in delayed emergence or

higher mortality of the overwintering insects. Nevertheless, there was a sufficient number of nesting individuals to determine that the new traps were

acceptable as nesting sites to some species, and that

they permitted photography of nesting behavior not

possible with the kind of trap used in my earlier study

(Krombein, 1967).

The traps I used earlier consisted of a hole drilled in

a stick of straight-grained white pine. Borings of four

different diameters were used: 3.2, 4.8, 6.4, and

12.7 mm. These traps were reasonably satisfactory in

my earlier work because I was unable to spend time in

the field observing nesting behavior. The prospect that

I would be able to make such studies in the near future,

however, led me to devise an improved trap to facilitate

field observations.

For this pilot study I used cavities of 4.8, 6.4, and

12.7 mm in diameter. The cavities were made by routing out a round-bottomed channel of one of those diameters in a long piece of straight-grained white pine.

The channels were routed to the same depth as the

Karl V. Krombein, Chairman, Department of Entomology,

National Museum .o/ Natural History,

Smithsonian Institution, Washington, D.C. 20560.

channel diameter. The pieces were then cut into 150-

mm lengths and one end of the channel plugged with

a short piece of wood. The 4.8- and 6.4-mm channels

were made in pieces of wood 20 mm wide and the

12.7-mm channels in pieces 25 mm wide. A piece of

clear Plexiglas ® y16" thick and cut to the same size

as the strip of wood was then taped against the channel. Finally, a plain strip of wood 6 mm thick and the

same length and width as the trap was fastened against

the plastic with rubber bands so that the whole assembly presented a light-tight simulated boring. The

trap components and their assembly are shown in

Figure 1. When used in the field, the plain strip of

wood could be readily removed to permit observation

and photography of the nesting behavior.

Bundles containing two traps of each diameter cavity were set out at 20 stations. The bundles were suspended from live or dead branches of turkey oak,

scrub hickory, or other trees (Figures 2, 4, 5), and a

few tied to a wooden frame supporting a Strophanthus

bush (Figure 3). The traps were inspected periodically

to determine when nesting began.

Table 1 presents records for the maximum and minimum temperatures and rainfall at the Archbold Biological Station during the period that nesting was

taking place. After the nests were gathered they were

held at 72°-74° F in the Station laboratory until the

morning of 27 April. From the morning of 28 April

until emergence of adult wasps the nests were held at

my home in Arlington, Virginia, where the temperatures ranged from maxima of 60°-70° to minima

of 50°-a)°.

I am most grateful to Richard Archbold and James

N. Layne of the Archbold Biological Station for mak1
FIGURES 1-5.—Archbold Biological Station, April 1969. Trap components: 1, 12.7-mm trap;

a, grooved wood stick, plexiglas ® strip and plain wood strip: b, plastic taped to grooved stick:

c, plain wood strip fastened to grooved stick and plastic to form a light-tight boring. Nesting

sites: 2, station 14, nest 107, Isodontia auripes; 3, nest 127, Isodontia auripes; 4, station 17,

nests 32 and 33, Podium rufipes; 5, station 10, nests 19 and 59? Trypargilum collinum collinum.
NUMBER 46

TABLE 1.—Maximum and minimum temperatures

and rainfall, Archbold Biological Station, Lake Placid,

Florida, 12-26 April 1969, as of 0900 hours on the date

of record

April

Trmptratures F" Rainfall

in inches

12

13

14

15

16

17

IK

I<J

20

21

22

23

24

25

Maximum

87

H'J

82

81

88

88

82

81

80

85

88

H8

82

Minimum

59

61

62

58

65

02

(.')

70

4<>

57

57

50

52

58

52

.04

1.37

. 14

ing available the splendid facilities and grounds during

my period of residence. I am indebted to the following

for identifications of prey used by the wasps and for

notes on the ecological niches occupied by the prey:

Willis J. Gertsch, Southwestern Research Station, Portal, Arizona, for the spider prey of Trypargilum c.

collinum; Ashley B. Gurney, U.S. Department of Agriculture, Washington, D.C., for the cockroach prey of

Podium rufipes; and Thomas J. Walker, University of

Florida, Gainesville, for the cricket and katydid prey

of Isodontia auripes. E. O. Bankmann of the Cabinet

Shop, Smithsonian Museum of Natural History, and

J. C. Widener of the Plastics Laboratory fabricated

the parts for the traps.

Isodontia (Murrayella) auripes (Fernald)

FIGURES 2, 3, 6-39

This sphecine wasp preys primarily on crickets (Gryllidae), but occasionally it also stores one or two shieldbacked katydids (Tettigoniidae) in the brood cell. I

was able to make observations on the nesting behavior

and development in two nests in 12.7-mm traps, numbers 127 and 107. Trap 127 and three others of the

same diameter (122, 125, 126) were set out 10 April

beneath part of a wooden frame (Figure 3) supporting

a Strophanthus bush in a cultivated field. I observed

carpenter bees, Xylocopa virginica krombeini Hurd,

emerging from borings in this frame, and I set out only

large traps in an attempt to induce nesting by these

bees. The other trap was set out 9 April beneath a dead

branch of a live scrub hickory (Figure 2) at the edge

of a fire lane through the slash pine-turkey oak association in a wooded area quite open to the sun. The traps

at both stations were about 1.5 m above the ground.

Nesting Behavior

I checked both of these stations several times a day.

The first evidence of auripes at either site was at 1145

on 12 April when I noted a female entering and leaving trap 125, flying around for a few seconds, then

entering trap 126, and finally leaving the area entirely.

Nesting had not begun in any of the traps at this station. At dusk that evening, 1845, this or another female

of auripes was resting inside trap 122. At 0815 on

14 April the sky was overcast and this female was still

in 122. On that same date by 1900 she was resting in

127 where she had brought in some pieces of grass stem

and blades. She was still in trap 127 at 0800 on

15 April. At 0925 the wasp was still inside the brood

cell and had begun to build up the closing plug. At the

already sealed inner end she had earlier constructed a

plug of compacted, coiled grass stems; it was

10 mm thick in the middle and 13 mm at the

edges. Two hours later I rechecked this trap and found

the wasp facing inward near the opening and compacting the materials forming a closing plug by pressing

with her head. My examination of her nest disturbed

the wasp, so that she turned around and flew out. The

brood cell, 80 mm long, contained a paralyzed falsejumping bush cricket (Orocharis luteolira T. J.

Walker) lying on its belly, head inward next to the

plug at the inner end; it bore a pale, yellowish-green

wasp egg. The temporary closing plug was 35 mm

long and was composed of loosely packed stems and

fibers in the inner 25 mm and densely compacted fibers

in the outer 10 mm.

My next visit to this station was an hour later, at

1240 on 15 April. During that period auripes brought a

second paralyzed specimen into the brood cell, a large

tettigoniid nymph (Atlanticus gibbosus Scudder),

which she placed on its belly, head inward next to the

bush cricket stored earlier. I removed the plain strip

of wood to permit photography through the plastic
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURES 6-10.—Nesting behavior of Isodontia auripes, nest 127, 1300-1315, 15 April: 6,

paralyzed cricket at outer end of trap, auripes making a passage through temporary closure;

7, auripes grasping cricket to carry it through temporary closure; 8, auripes dragging cricket into

brood cell; 9, auripes ovipositing on cricket; 10, auripes sealing temporary closure.
NUMBER 4 6

and could see the abdomen of this tettigoniid pulsating

rhythmically. I was unable to see whether it bore a

wasp egg. Shortly after 1300 the auripes returned

with another paralyzed bush cricket, which she left

venter down in the outer 30 mm of the trap while

she excavated a passage through the closing plug

(Figure 6). She entered the brood chamber, pushed

the earlier prey closer together, turned around and

went out through the closing plug head first. Turning

around again, she grasped the head end of the cricket

with her mandibles (Figure 7), and carried it venter

down through the passage in the closing plug. Once

inside the brood chamber, she dropped the cricket,

turned around on her back, grasped the head end of

the cricket with her mandibles (Figure 8), and dragged

it up above the tettigoniid nymph. Then, continuing

to lie on her back, she turned the cricket on its side,

curled her abdomen upward (Figure 9) and deposited

an egg between the fore and mid coxae. Next, she t

pushed this cricket, now venter up, to the inner end

of the brood chamber on top of the first two prey

(Figure 11). About 1315 she left the brood chamber,

pulled out some fibers from the outer end of the plug,

and proceeded to work on the plug to form a tighter

closure (Figure 10). At 1327 she flew away, leaving

some loose fibers in the outer 40 mm of trap 127.

Exposing the nest to light and using the electronic flash

for photography did not appear to affect the behavior

of the wasp in 127 whatsoever. This auripes had not

returned by 1335.

Upon my next inspection of nest 127 at 1440 on

15 April, I discovered that the wasp had brought in

a fourth cricket. She had also dragged the third cricket

down from on top of the tettigoniid nymph and placed

it on its back behind that prey. She flew back to the

nesting site at this time, apparently not carrying any

prey, and flew off in a few seconds without entering

the nest. The wasp was not in the nest at 1545, but

at 1845 she was resting there for the night, facing

outward in the outer end of the boring, with her abdomen against the closing plug. She left the nest before

0830 on the 16th, and sometime during the morning

she brought a fifth cricket into the nest (Figure 12).

There was no further nesting activity at 1240 or 1330,

so I brought the nest into the laboratory for further

photography and weighing of the prey. This wasp

never began a second nest at this station, even though

empty traps were available.

Another female auripes began a nest in trap 107,

FIGURES 11-12.—Nest 127, Isodontia auripes: 11, cricket

bearing wasp egg on top of tettigoniid, 1330, 15 April; 12,

rearrangement of prey after fifth prey was brought into nest,

1440, 16 April.

half a kilometer distant from trap 127, during the 3-

day period 12-14 April. When I checked Station 14

at 0900 on the 15th, I found that trap 107 contained

a plug of compacted Spanish moss strands 5 mm thick

at the inner end, an empty brood cell 65 mm long, and

a temporary closure of tightly packed Spanish moss

about 15 mm thick. Trap 108, adjacent to 107, contained a few short strands of Spanish moss near the

inner end; there was no subsequent nesting activity

in the former trap, so it is likely that the wasp nesting

in 107 may have placed the moss in 108 before or

during preliminary nesting activities in 107. While I

was examining the traps, a large insect, possibly the

Isodontia, buzzed around my head and flew off before

I could identify it.

The female auripes was in the outer end of nest 107

at 1350 on 15 April. She flew off when I shone a

flashlight into the trap. At this time the nest contained

three paralyzed false-jumping bush crickets lying on
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURES 13-14.—Isodontia auripes, nest 107: 13, 1550, 15 April, showing nest architecture and

prey; 14, same as 13 but 1050, 16 April.
NUMBER 46

their backs, head inward, each bearing a pale yellowish-green wasp egg affixed to the venter of the thorax.

I returned to 107 at 1415 and for the next 15 minutes

I watched the wasp bringing in plant materials to add

to the temporary closure. At 1421 she carried in a

piece of grass stem about 5 cm long. It took her 2

minutes to work this into the plug, after which she

flew around the immediate vicinity, alighting here

and there on dead plants, and trying unsuccessfully

to pull off some of the curled, dried leaves. In a few

minutes she brought in a piece of Spanish moss about

8 cm long, worked it into the plug for 3 minutes, and

then flew out of sight. When I returned at 1551, she

flew out of the trap, and I discovered that she had

brought in a fourth cricket during the interim and had

laid an egg on it (Figure 13). At 1850 that evening

she was resting at the outer end of the trap with the

tip of her abdomen against the temporary closure;

there were still only four bush crickets in the brood

cell.

The wasp had already left 107 when I made my first

check of that nest at 0820 on 16 April; the nest appeared the same as it had the previous evening. Five

minutes later the auripes alighted for an instant at

the nest entrance and then flew off; she carried neither

prey nor vegetation. The wasp flew out of 107 when

I returned half an hour later; again, there had been

no nesting activity in the interim. The wasp did not

return during the next half an hour. However, by 1045

there had been additional nesting activity (Figure 14).

One of the earlier prey specimens had been piled on

top of the first one at the inner end, another prey had

been brought in, and the wasp had left a pile of loose

FIGURE 15.—Isodontia auripes, nest 107, loose vegetation at

nest entrance, 1900, 16 April.

371-049 O—70 2

vegetation (Figure 15) at the trap entrance. I checked

107 several times during the afternoon, before removing the nest at 1600, and noted no additional nesting

activity. However, subsequent examination in the laboratory disclosed that a sixth prey had been stored

during the 16th.

Nest Architecture

Figure 14 shows the architecture of a nearly completed auripes nest with a narrow plug of vegetable

fibers at the inner end, a brood cell, and a thicker

closure of vegetable fibers thoroughly compacted in the

outer portion of the plug. It is quite likely that neither

of these nests had been completed when I picked them

up during the afternoon of 16 April. Normally, when

auripes makes a final closure, she brings in grass

stems and blades which she places along the axis of

the boring at the outer end, protruding from the

entrance (Krombein, 1967, p. 247).

The plug at the inner end of the boring in 127 was

about 12.5 mm thick and consisted of tightly coiled and

compressed grass stems and blades (Figure 16);

whereas, in 107 the plug was 5 mm thick and made

from coiled, compacted strands of Spanish moss (Figure 18). The brood cells were 57 mm long in 127 and

64 mm in 107. The closing plug of 127 was 41 mm

thick and was composed of pieces of dried vegetable

fiber and grass blades, loosely packed on the inner

(left) half and firmly compacted on the outer half

(Figure 17). In nest 107 the closing plug was of the

same thickness: the inner, loosely packed half was

made from strands of Spanish moss, the outer, closely

compacted half from small pieces of plant stems having rather long woolly hairs (Figure 19).

Prey

These two individuals of auripes preyed principally on

the false-jumping bush cricket Orocharis luteolira T.

J. Walker (Figure 20) and, less frequently, on the

shield-backed katydid Atlanticus gibbosus Scudder

(Figure 21). The wasp in 127 used only adult

Orocharis and a nymph of Atlanticus; whereas, the

wasp in 107 used both nymphal and adult Orocharis

and nymphal Atlanticus. Both sexes of Orocharis were

preyed upon, but only nymphal males of Atlanticus.

Dr. T. J. Walker, who was able to identify both

prey species from fragments remaining in the nests
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

18

KS pil l Jj&Jm

BRIE

19

FIGURES 16-19.—Isodontia auripes, details of nest architecture, 16 April: 16, plug at inner end

of nest 127; 17, closing plug, nest 127; 18, plug at inner end of nest 107; 19, closing plug,

nest 107.

and from photographs, commented that in his experience Orocharis never descends to the ground whereas

Atlanticus nymphs seldom ascend from the ground,

especially during the day when auripes would be

hunting for prey. This suggests that auripes exploits

several ecological niches while hunting for prey.

All specimens of prey were thoroughly and permanently paralyzed, and were capable of only weak reflex

actions of their antennae, mouthparts, and legs. Feces

were voided for a day or two after the prey were stored.

In nest 127 each of the crickets lacked a hind leg; these

may have been amputated by the wasp.

Table 2 presents information on the prey stored in

these nests: their sex, identity, length, and their fresh

weight after voiding feces. The specimens are listed in

the order in which the wasp arranged them in the nest,

127-1 being the prey at the inner end on the bottom

and 127-5 the prey nearest the outer end. It should be

remembered, however, that both wasps did some shifting around of specimens subsequent to the prey being

brought into the nests. Consequently, it must not be

TABLE 2.—Identity, length, and weight of false-jumping bush crickets and shield-backed katydids stored in

nests of Isodontia auripes (Fernald).

Prey

number

127-1

127-2

127-3

127-4

127-5

107-1

107-2

107-3

107-4

107-5

107-6

Prey identity

Orocharis, adult 9

Atlanticus, nymphal d*

Orocharis, adult d*

Orocharis, adult ?

Orocharis, adult ?

Orocharis, adult d1

Orocharis, nymphal ?

Orocharis, adult ?

Orocharis, nymphal 9

Atlanticus, nymphal <j*

Atlanticus, nymphal d"

Length

in mm

17

16

14

17

15

15

12

17

11

13

14

Fresh

weight

in mg

190

290

120

190

140

120

95

185

110

115

215

assumed that the order in which I list them is necessarily the order in which they were caught. Prey specimens 127-1, 3, and 5 each bore a wasp egg, as did the
NUMBER 46

FIGURES 20-21.—Prey of Isodontia auripes, nest 127, dorsal

view: 20, false-jumping bush cricket, Orocharis luteolira,

adult 9 ; 21, shield-backed katydid, Atlanticus gibbosus,

nymphal £ .

first five of six prey in 107; these eggs added an infinitesimal amount to the fresh weight of the prey. The

mass fresh weight in nest 127 was 930 mg or 310 mg

for each wasp egg; similar figures for nest 107 were 840

mg and 168 mg.

I captured a pair of adult Orocharis luteolira which

had spent the night in two empty traps. The female was

18 mm long, the male 17 mm, and the fresh weights

were 239 mg ( $ ) and 166 (o* ) before voiding feces.

Each was held for 24 hours, then killed and dried

thoroughly in an oven. The resultant dry weights were

67 and 49 mg respectively, a weight loss of a little over

70 percent. Applying that reduction factor to the

average weights of prey stored per wasp egg, it is

calculated that 93 mg dry weight was provided per egg

in nest 127 and 50 per egg in nest 107.

FIGURE 22.—Isodontia auripes, egg on adult male, Orocharis

luteolira, 1600, 16 April.

Adults of auripes were so uncommon that I was not

able to capture and weigh any of them. However, I did

obtain a series of six female and male Isodontia

(Isodontia) exornata Fernald, a species of comparable

size. These specimens were 17-19 mm long and had

fresh weights of 80-123 mg. After thorough drying in

the oven, the resultant dry weights were 28-48 mg, a

reduction of 61-65 percent.

Life History

The sausage-shaped eggs were slightly curved, pale

yellowish green, 3.4 mm long and 0.75 mm wide. The

anterior end was glued firmly behind the fore coxa and

the egg was placed transversely across the sternum so

that the posterior end extended beyond the side of the

thorax opposite the egg attachment (Figure 22). In

nest 127 two of the eggs were attached behind the

right fore coxa, one behind the left; in 107 four eggs

were attached behind the left fore coxa and only one

behind the right.

Larvae hatched from the eggs in 52-54 hours in the

five cases where reasonably close information was available on the times of oviposition and hatching. Body

segmentation was visible through the chorion for several hours before hatching occurred. The newly

hatched larvae began to suck blood at the point of

attachment of the egg. Feeding was slow in the younger

stages, and the larva required about two days to empty

completely the prey on which the egg has been laid.

I photographed the development of the youngest larva

in nest 107 at periodic intervals over this 2-day period
10

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

30

FIGURES 23-30.—Youngest larva in nest 107, Isodontia auripes: 23, newly hatched larva, 1130,

18 April; 24, 1630, 18 April; 25, 2000, 18 April; 26, 0820, 19 April; 27, 1125, 19 April:

28, 1935, 19 April; 29, 0800, 20 April; 30, 1155, 20 April, prey so hollowed out that it broke

in two when lifted out of brood cell.
NUMBER 46 11

FIOURES 31-34.—Larvae in brood cell, nest 107, Isodontia auripes: 31, larvae still feeding inside

prey on which eggs were laid, 1225, 20 April; 32, same as 31, but 2000, 20 April; 33, larvae at

inner end feeding on prey parts, larva at outer end still feeding internally on original prey, 0800,

21 April; 34, all larvae feeding externally, 2000, 21 April.
12

(Figures 23-30). The prey had been so thoroughly

gutted by the end of the second day that the head and

anterior part of the thorax separated from the rest

of the body when I removed the specimen from the

nest. After emptying the body contents, each wasp

larva continued to feed on the exoskeleton, devouring

almost all of it but fragments.

When the older larvae finished feeding on the original specimen of prey, they wriggled to one of the untouched prey, if any, and began to feed on it (Figures

31-32). Thus, the two older larvae in 127 finished their

original crickets at 0800 on 20 April; by 1155 one of

them commenced to feed with its head inside the

abdomen of the tettigoniid nymph, and by 1600 both

larvae were feeding through the thorax of the two

prey specimens which did not originally bear eggs. The

larvae in both nests continued to feed on fragments of

the exoskeletons for the next day or two (Figures 33-

34). On 22 April at 0800 the three larvae remaining

in 107 finished feeding and began to pull strands of

Spanish moss into the brood cell (Figure 35); they

continued to pull Spanish moss into the cell until at

least 1600 (Figure 36). The two larger larvae in 127

continued to feed on prey fragments until 0800 on 23

April. By midmorning one of these larvae had caught

the anterior end of its body in the hollowed out thorax

of the tettigoniid and was unable to extricate itself; it

died several days later. The larvae in 107 consumed all

of the prey except for parts of the exoskeleton whose

dry weight totaled 55 mg; in 127 the larvae left uneaten

108 mg dry weight.

The three larvae in 107 and one larva in 127 began

spinning cocoons between 1900 on 23 April and 0800

on 24 April. The cocoons were constructed among

pieces of dried plant materials which the larvae pulled

from the inner end of the closing plug and among the

fragments of the prey (Figures 38-39). The larvae had

not been spinning for too lengthy a period by 0800 because they could still be seen through the white silken

cocoon walls at that time (Figure 37). By 1915 on 24

April the walls of the white inner cocoons were so

dense that the larvae could not be seen through them.

On the following morning at 0800 the inner cocoons

were light tan, indicating that the larvae had impregnated them, probably with liquid fecal wastes. No information was obtained on the date of pupation

because I did not open the cocoons. A male auripes

emerged from nest 107 on 7 June and a female from

m-st 127 on 8 June. Thus, the life cycle from egg to

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

adult in these nests was about 54-55 days.

There was a high mortality rate in both nests but

very little, if any, was due to cannibalism. In nest

127 where there were three eggs, the youngest egg

never hatched and one of the mature larvae died after

getting stuck in the hollowed-out thorax of a prey. In

nest 107, where there were six eggs, one larva died

two days after hatching, the youngest larva (the subject of Figures 23-30) died from lack of food, two

larvae died in cocoons, and one adult emerged. The fate

of the sixth larva in 107 was not ascertained. It just disappeared one day and may have been cannibalized.

Podium rufipes (Fabricius)

FIGURES 4, 40--61

A single female of this cockroach-preying wasp stored

two nests (33, 32) in 4.8-mm traps on successive days.

The traps were suspended on 9 April beneath the limb

of a live scrub hickory (Figure 5) at the edge of a fire

lane through slash pine-turkey oak association in a

wooded area quite open to the sun. The station (#17)

was 1.5 in above the ground with the trap entrances

facing northeast.

Nesting Behavior

A rufipes female was at this station when I inspected

the traps at 1035 on 21 April. She did not enter any of

the traps while I was there but crawled over them for

a few seconds and then flew off. All of the traps were

empty at that time. I remained at the station for 20

minutes expecting that she might return for further

inspection or with a cockroach, but she did not reappear. I rechecked the traps at 1310 and again at 1640,

but no prey had been brought in during the interim

periods.

During my next check of this station at 1030 on

22 April, I found that this or another female had

placed a paralyzed cockroach nymph at the inner end

of trap 33. The cockroach was lying on its back, head

inward, and the wasp egg was attached on the mid line

behind the fore coxae. There was no temporary plug

at the nest entrance. Presumably the cockroach had

been brought in earlier on the 22nd, inasmuch as the

trap was empty at 1640 the previous day. I remained

at this station until 1115, but the Podium did not

return to the nest during that 45-minute period. Upon
NUMBER 4 6 13

FIGURES 35-39.—Larvae in brood cell and cocoons, nest 107, Isodontia auripes: 35, larvae

pulling moss from closing plug, 0800, 22 April; 36, same as 35, but 1605, 22 April; 37, larvae

spinning cocoons, 0800, 24 April; 38, cocoon before removal of pieces of Spanish moss in which

it was spun; 39, cocoon after removal of most of Spanish moss.
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

returning at 1345,1 found that the wasp had brought

in six more paralyzed cockroaches. The prey were

all lying head inward, more or less on their venters,

and with the anterior end of each prey resting on the

abdomen of the preceding individual.

I removed the plain strip of wood from the trap at

1345 to photograph and observe activities through the

plastic. At 1348 the wasp flew onto the set of traps, and

ran around on the ends of the sticks in a confused

manner, searching for her nest. After a few seconds

she recognized the nest, entered head first bearing the

cockroach venter down and head first clasped in her

mandibles, placed it with the head end on the abdomen of the preceding prey, backed out of the nest, and

flew off immediately. At 1355 she returned directly to

the traps with another cockroach, began to enter the

nest, but was frightened off when I approached closely

and took a flash picture. She flew around for a few

seconds, then returned and took her prey into the nest.

She backed out and flew off at 1358. Twelve minutes

later she returned with another cockroach, alighted on

the end of the traps, crawled in head first, bearing the

prey as described above, deposited the prey, and then

backed out and flew off.

Half an hour later, at 1428, she flew back without a

cockroach, entered the outer end of the boring for a

second, and then flew off. I assumed that she might

now be ready to plug the nest for she had amassed

nine prey. However, at 1449 and 1529 she returned to

the nest, carrying neither debris to construct a plug nor

additional prey, peered into the nest for a second or

two and then flew off. At 1545, after her fourth such

visit, I replaced the plain strip of wood and left the

area.

Upon returning to this station at 1900,1 found that

during the preceding three hours the rufipes had

brought in two more cockroaches and had constructed

the closing plug. Inasmuch as construction of the closing plug is a lengthy process, it is probable that the

nest was completed just a short time before 1900. The

wasp was not in any of the other traps at this station

nor in the immediate vicinity. I removed the completed nest, placed trap 34 in the position occupied

by 33, and put an empty trap (32) from an adjacent

station in the position occupied earlier by 34.

On the morning of 23 April, I checked all of the

other stations before returning to station 17 at 1045.

At that time there was a small paralyzed cockroach

at the inner end* of trap 33, lying on its back, head

inward, and bearing the wasp egg behind the right

fore coxa. The rufipes female, most probably the same

individual that constructed nest 32, alighted on the

end of the traps at 1100 without a cockroach. She

seemed to have difficulty locating her nest, probably

because I had removed the strip of wood covering the

plastic. In a few seconds, she found the nest, poked

her head inside, and then flew off. She did not return

by 1130, so I replaced the strip of wood and left the

area.

When I returned at 1311, there was a second cockroach in the nest, venter down, head inward, pushed

up onto the abdomen of the small cockroach bearing

the egg. At 1318 the wasp flew directly to the trap

entrances, walked around in some confusion for a few

seconds trying to find her nest because I had again removed the plain strip of wood from the plastic. Finally

she entered, carrying a cockroach dorsum up beneath

her (Figure 40) and pushed the prry up onto the

abdomen of the second prey. I could not ascertain how

she held the cockroach while she was in flight with it.

When she entered the nest, she was definitely pushing it

ahead of her, using only her mandibles to manipulate

it. She backed out of the nest immediately, downward onto the end of the trap and then flew off.

At 1331 she flew in with another cockroach, but

was frightened away when I arose to take a photograph. She flew back several seconds later but was so

disoriented that she placed this prey dorsum up and

head inward at the inner end of trap 74 rather than

in trap 32. After she flew off, I plugged the entrances

to the other three traps containing 4.8- or 6.4-mm

borings so that she would not make this error again.

She alighted on top of the traps at 1348 but was not

carrying a cockroach and flew off immediately. At

1355 she returned with another prey and placed it on

its belly, head inward next to the third cockroach

brought into 32 (Figure 41). The wasp transported

the prey within the nest by clutching it with her long,

slender, slightly curved mandibles which fitted into

the notch on each side of the thorax between the pronotum and mesonotum.

A period of about an hour now ensued during which

the wasp without prey visited the nest momentarily at

1405, 1444, 1510, 1527, and 1548. Usually she flew in

and alighted directly on the traps, but on one occasion

she alighted first on the limb from which the traps

were suspended. Upon each of these visits she either

put her head inside the entrance and palpated with
NUMBER 4 6 15

FIGURES 40-41.—Podium rufipes carrying paralyzed cockroach nymphs into nest 32, 23 April:

40, third prey, Latiblatella rehni, 1318; 41, fifth prey, Chorisoneura sp., 1355. Note that cockroach is transported by the mandibles only.
16 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

her antennae or went a couple of centimeters into the

boring and then flew off.

At 1608 she brought in prey again, but was frightened off three times by my attempts at photography.

In the quick glimpses I caught of her at this time, it

appeared that she might be carrying the cockroach

with her mandibles and forelegs. Finally, she took in the

cockroach and left it about 2.5 cm away from the

preceding prey. At 1624 she brought in another prey

which she placed on the abdomen of the previous

specimen. And, at 1636 she flew in with another very

large cockroach which she had difficulty stuffing into

the boring.

After pushing this last cockroach up against the

previous prey, rufipes backed out and wandered

around on the traps, twice putting her head and antennae into the entrance to nest 32. She flew off after a

few seconds and returned at 1639 with a piece of

debris which she placed 13 mm inside the entrance.

At 1647 she returned without debris, poked her head

in for a second and flew off. Then at 1649, 1652, and

1656 she brought in additional loads of debris which

she shoved against the first without attempting to compact the mass. At 1659 she alighted on the hickory

trunk and in a few seconds flew onto the traps. She

did not carry any debris this time and just inspected

the plug before flying off again.

At 1702 she returned with a larger load of debris

and now she began to compact the various loads. For

about half a minute she perched on the end of the

trap in various positions, rotating around the entrance

and tapping lightly with her mandibles against the mass

of debris. At 1705 she was back with another large

load which she compacted with the same light pecking

FIGURE 42.—Podium rufxpts compacting sand in closing plug of nest 32, 1729, 23 April. Note

that the extended left mandible is visible just below the left foreleg.
NUMBER 46 17

movements for 45 seconds. These latter two larger loads

of debris consisted of caterpillar frass spun loosely

together with silk. Probably she obtained this mixture

of frass and silk from the retreat of a leaf-roller or

leaf-tier caterpillar.

The shadows were beginning to lengthen as the sun

lowered, and the rufipes now began the next step in

the construction of the complex closing plug, bringing

in her mandibles damp sand which later dried to

form a firmly agglutinated layer. The first lump was

taken to the nest at 1710 and applied to the surface of

the debris carried in earlier. This and successive loads

of damp sand were spread over the surface of the plug

and tamped in with rapid, light pecking taps with the

opened mandibles, the head being held in the normal

downward position (Figure 42). To compress the

sand evenly the wasp rotated around the entrance. I

frightened the wasp away at 1716 when I attempted

to photograph her arrival with the next load of sand.

She brought in additional lumps of damp sand at 1725,

1729, 1736, 1744, 1751, 1759, and 1804; at 1750 she

visited the nest but did not bring in sand. She compacted each load of sand with light blows of the extended mandibles for about a minute, although

occasionally the tamping lasted as long as two minutes

or as little as 30 seconds. Usually she alighted on the

traps and crawled rapidly to the entrance, but occasionally she alighted on the tree trunk and then made

a short flight onto the traps.

The final stage in the nest closure began at 1811

when she arrived with a large lump of clear, sticky

pine resin in her mandibles. She smeared this over

part of the layer of damp sand. She carried in additional lumps of resin at 1815, 1820, 1828, and 1833.

These were smeared over the surface of the sand and

compacted with more deliberate pecking movements

with her opened mandibles for 1-1J4 minutes per load.

The sun had gone down behind the ridge by 1830, so

that it was dusk when she brought in the last few loads

of resin. When the wasp did not return by 1841, I

picked up the nest, assuming that she had completed

the closure.

I revisited this station at 0820 on 24 April to set out

a replacement trap for nest 32. The wasp apparently

had finished the plug on the previous evening, for

there was no resin at the entrance to any of the other

traps. I checked the traps at this station several times

daily through 26 April, but the rufipes never returned

to begin another nest.

Nest Closures

Nests 33 and 32 were examined and photographed in

the laboratory on the evenings of 22 and 23 April respectively. The closing plug of nest 33 (Figure 43) was

10.5 mm thick, the inner debris being capped by a

layer of agglutinated sand 0.5 mm thick and an outer

layer of clear pine resin 1 mm thick. The debris at the

inner end consisted of some dry hollowed-out spider

parts, bits of spider web, particles of rotten wood, some

fine brown fibrous material and then more rotten

wood.

The plug of nest 32 (Figure 44) was 12.5 mm thick,

the inner debris being capped by a layer of agglutinated

sand 0.5 mm thick and by an outer layer of clear pine

resin of the same thickness. The debris at the inner

end consisted of some particles of rotten wood, then

large clumps of caterpillar frass fastened together with

silk, followed by a few more fragments of rotten wood.

FIGURES 43-44.—Closing plugs of Podium rufipes nests: 43,

nest 33; 44, nest 32.
18

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURES 45-53.—Prey and egg placement, Podium rufipes: 45, inner end (at left), nest 33,

note egg on innermost cockroach; 46, inner end (at right), nest 32, note egg on innermost

cockroach; 47, prey in nest 33, note innermost cockroach lying on its dorsum, the others lying

on their venters; 48, egg on Latiblatella rehni nymph, nest 33; 49, egg on Chorisoneura sp.

nymph, nest 32; 50, Latiblatella rehni nymph, dorsal, nest 33; 51, Chorisoneura texensis adult,

dorsal, nest 33; 52, Chorisoneura sp. nymph, dorsal, nest 33; 53, Eurycotis floridana nymph,

dorsal, nest 33.
NUMBER 46 19

Prey

The placement of prey in both nests was identical. The

fust cockroach brought into each trap was placed on

its back, head inward at the inner end of the boring,

and the wasp egg was laid on it before additional prey

were stored (Figures 45-46). Subsequent cockroaches

were brought into the nest head first and venter down

and stored in that jwsition. Usually the subsequent prey

were shingled, so that the head end of one cockroach

rested upon the abdominal dorsuin of the preceding

cockroach (Figure 47). The legs of almost all of the

cockroaches were complete, indicating that ruftpcs

seldom or never practices amputation.

I did not observe storing of the first cockroach and

oviposition. Consequently, it must still be ascertained

whether the wasp carries the first cockroach into the

nest venter up, or whether the wasp turns this first preyover after placing it at the inner end of the boring.

In either case, before ovipositing, the wasp would

have to back out of the nest, turn around, and back

into it, so that the egg could be placed in the proper

position.

Three or possibly four species of prey were stored in

the nests as follows: nymphs of Latiblatella rehni

Hebard (Figure 50), adults of Chorisoneura texensis

Saussure and Zehntner (Figure 51), nymphs of

Chorisoneura sp. probably texensis (Figure 52), and a

nymph of Eurycotis floridana (Walker) (Figure 53). I

did not observe hunting behavior, but presumably the

wasp flushes the cockroaches from their daytime retreats, most likely among fallen leaves or other vegetation on the ground.

Table 3 presents information on the prey stored in

these nests: their identity, their length, and their fresh

weight. The specimens are listed in the order in which

they were placed in the nests, 33-1 being the first cockroach taken into nest 33 and 33-11 the last. The

weights of 33-1 and 32-1 include the very infinitesimal

weight of the wasp egg which could not be removed

without danger of injury. Cockroach 32-4 is the one

which was mistakenly placed in trap 74. The mass

weight of cockroaches in nest 33 was 347 mg, with an

average weight of 32 mg. In nest 32 similar figures were

310 and 34 mg respectively. A male wasp developed in

each of these nests.

All of the cockroaches were thoroughly paralyzed

and exhibited only relatively weak reflex actions of

their antennae, mouthparts, and legs. The prey bearing

the egg was no more heavily paralyzed than the other

TABLE 3.—Identity, length, and weight of cockroaches

stored in nests of Podium rufipes (Fabricius)

Prey

number

33-1

33-2

33-3

3 3 ^

33-5

33-6

33-7

33-8

33-0

33-10

33-11

32-1

32-2

32-3

32-4

32-5

32-6

32-7

32-8

32-9

Prey identity

Latiblatella nymph

Latiblatella nymph

Latiblatella nymph

Chorisoneura nymph

Chorisoneura adult

Latiblatella nymph

Latiblatella nymph

Eurycotis nymph

Latiblatella nymph

Chorisoneura adult

Latiblatella nymph

Chorisoneura nymph

Chorisoneura nymph

Latiblatella nymph

Latibtatella nymph

Chorisoneura nymph

Chorisoneura nymph

Chorisoneura nymph

Latiblatella nymph

Latiblatella nymph

Length

in mm

10.5

8.0

10.5

7 . 0

9.0

7.0

10.5

6 . 0

7.5

9 . 0

11.0

6 . 0

5.0

11.0

10.5

8.0

7.5

7.0

10.0

11.0

Fresh

weight

inmg

52

24

46

17

21

19

46

17

25

27

56

13

8

59

57

20

20

15

59

60

cockroaches. The cockroaches also continued to void

feces as may be noted in Figure 54.

Life History

The eggs were sausage shaped, 2.67 mm long and

0.67 mm wide. The head end was glued firmly to the

intersegmental membrane just to the left of the midline and behind and somewhat beneath the left fore

coxa. The left leg was displaced slightly in a larger

cockroach (Figures 45, 48) and rather noticeably in

a smaller specimen (Figures 46, 49). The eggs extended backward to the apices of the mid or hind

coxae.

The egg in nest 33 hatched between 1930, 24 April,

and 0800, 25 April, and that in nest 32 between 1700

and 2030, 25 April. Assuming that the latter egg may

have been laid about 1000 on 23 April, we can estimate, that egg hatch occurs in 55-56

 l/i hours when it

is held at about 80°-88° for 9 hours and at 72°-74°

for the remaining time. Judged from the hatching data

recorded for the egg in nest 32 and the fact that the
FIGURES 54-61.—Larval development, Podium rufipes, nest 33: 54, young larva about 16 (?)

hours after hatching, 1150, 25 April; 55, 1150, 26 April; 56, 1930, 26 April; 57, 0930, 28 April;

58, 0700, 29 April; 59, 0720, 30 April; 60, 0645, 1 May; 61, 0720, 2 May.

egg in nest 33 was laid just about 24 hours earlier, we

can postulate that egg hatch in nest 33 probably occurred shortly after 1930 on 24 April.

The anterior end of the egg was glued to the intersegmental membrane between the fore and mid coxae.

It appeared that the chorion may not be shed until

the larva makes some growth, because slight rhythmic

contractions were visible posteriorly in the egg in nest

32 at 2030 on 25 April, indicating that feeding had

begun. After the larva hatched, it penetrated the cockroach body between the fore and mid coxae and began

to suck blood.

The egg-bearing cockroach in nest 32 still exhibited

some reflex movements at 0845 on 26 April, a little
NUMBER 46 21

more than 12 hours after the larva commenced feeding, but it was quiescent and probably dead by 1915

on that same date. One cockroach in nest 33 exhibited

reflex movements as late as 0900 on 28 April, before

the wasp larva fed on it and almost 6 days after it

was paralyzed.

The newly hatched larvae developed slowly at first

(Figures 54-56). If the assumption as to the probable

hatching time of the larva in nest 33 is correct, then

Figure 54 was taken about 16 hours after hatch; note

that the larva is noticeably thicker than the egg (Figure 48), but no longer. Figures 55 and 56 were taken

of this same larva 24 and 32 hours after Figure 54;

note that the larva has increased in girth during these

periods but has not become longer. The larva in nest

33 continued to feed with its head inside the first cockroach until 28 April. By 0900 on that date (Figure 57)

it had consumed all of the first cockroach except for

the cxoskcleton.

Development was now much more rapid. By 0700

on 29 April the larva in nest 33 had gutted the second

cockroach in the nest (Figure 58). A day later there

were only four whole cockroaches left out of the original eleven (Figure 59). On 1 May at 0645 there was

only one untouched cockroach (Figure 60). At 0720

on 2 May the larva was feeding on just exoskeletal

remains (Figure 61), which it continued to do until

that evening when only very small fragments remained.

Larval feeding in nest 32 followed a similar pattern

except that the larva gutted the small first cockroach

more quickly and was feeding internally on the second

by 0900 on 28 April. There were only two large and

one small prey untouched at 0640 on 1 May, and only

one large cockroach at 0715 on 2 May. By 1945 that

evening there were only exoskeletons remaining, and,

except for tiny fragments, these had all been consumed

by 0825 on 4 May.

Thus, the larval feeding period was about 8 days in

nest 33 and 8/a in nest 32, although 37 mg more

of food (the equivalent of one moderate-size cockroach) was provided for the former. The discrepancy

is undoubtedly due to the larva in nest 32 being subjected to the cooler Arlington temperatures a day

earlier in its developmental cycle.

Regrettably, I was unable to obtain information on

the number of larval instars. The manner of feeding

during the early stages, with the head buried inside the

cockroaches, precluded periodic measurements of the

head capsule. I was never fortunate enough to witness

the shedding of the cuticle at a molt.

Construction of the cocoon in nest 33 required about

2/ 2 days. By 1800 on 3 May the larva had pulled some

of the looser debris from the.inner end of the closing

plug about 25 mm further into the boring. It had

also begun to construct a network of silken threads

in which to suspend the cocoon at the inner end of the

boring against the plastic and sides of the boring. On

the following morning at 0825 there was an opaque,

fusiform white cocoon at the inner end; no feces had

been voided. Most of the loose debris was now at the

extreme inner end of the boring and some was attached

to the anterior end of the cocoon. By 1925 the larva had

coated the cocoon walls with light-tan liquid feces,

and it was still moving inside the cocoon. The next

morning at 0705 the cocoon was darker brown, still

soft and the larva was still working inside. By 0630

on 6 May the cocoon walls were dry and brittle, and

the wasp larva was lying motionless inside. Cocoon

construction in nest 32 was done in the same manner

and required the same amount of time.

On 8 May at 0645 I removed part of the anterior

end of the cocoons in nests 33 and 32. The resting

larva in the former was quiescent, but that in the latter

wriggled forward out of the cocoon; a little later it

wriggled back into the cocoon. Pupation occurred in

nest 33 between 0630 and 1830 on 21 May, and

between 2200, 22 May, and 0600 on 23 May in nest

32. Eclosion of the adult male wasp occurred 15 June

in 33; this adult left the nest 18-19 June. In nest

32 the adult male wasp left the nest 19-20 June.

Discussion

The evidence offered by these observations does not

permit a determination as to how a female rufipes

knows how much prey to store in a nest to bring a

larva to maturity. Judged from these data alone, one

might speculate that about 9-11 cockroaches are required to bring one larva to maturity. In my earlier

lengthy account of this species (Krombein, 1967,

pp. 251-255, figs. 62-63), however, I mentioned that

nests from North Carolina and Florida contained 3-16

cockroaches. Consequently, it does not appear that the

number of prey stored is likely to be the determining

factor. An alternative possibility is that the wasp has

some sort of internal calculating device to gauge the

amount of prey stored by the cumulative weight of the

individuals brought into the nest. It will be recalled
22

that these two nests each contained about a third of a

gram fresh weight of cockroaches. Many more observations of freshly stored nests will be needed to determine

if provisioning by weight is a plausible hypothesis.

There is another possible explanation concerning

the number or weight of prey stored; namely, that

the wasp calculates neither the mass nor the number,

but that the number of prey stored is entirely dependent upon the success of the wasp in finding cockroaches

during a single day. It should be recalled that both

nests were begun relatively early in the morning, perhaps about 1000, and that the complex closing plug

was begun late in the afternoon as the light intensity

began to decrease rapidly. One must also remember

that the wasp apparently hunted fruitlessly for cockroaches for extended periods during the day, judged

from the numerous preyless visits she made to the nest.

Can it be that rufipes begins each nest early in the day,

stores it with as many cockroaches as she can find during the day, and then constructs the closure, regardless

of how many prey have been stored, as soon as the

decreasing light intensity imposes a requirement for

closing the nest? Podium rufipes does not spend the

night at the nesting site as do many other wasps; this

could very well dictate that the nest must be plugged

at the end of the day. Again, many more observations

will be needed to ascertain the validity of this theory.

Figure 62 in my earlier account of rufipes (1967)

is a photograph of the prey lying in a nest from North

Carolina, showing all of the cockroaches, including

the one bearing the wasp egg, lying on their backs

head inward. In contrast, in the two Florida nests reported here, only the cockroach bearing the egg was

on its back, all of the rest were venter down. Additional field observations are needed to ascertain whether the former method of prey storage is characteristic

of the North Carolina population, or whether either

manner of prey storage is an individual idiosyncrasy.

I saw no parasites during my lengthy observations

at the nest site, and no infestation developed in the

nests after they were brought into the laboratory. Actually, rufipes is very subject to parasitism by the

cuckoo wasp Neochrysis panamensis (Cameron).

In my account of the latter species (1967, pp.

473-475), I mentioned that it was found in 21 rufipes

nests from the Archbold Biological Station in Florida,

a parasitism rate of 36 percent. Access to the rufipes

nests is very simple because there is no temporary

closure, such as that made by Isodontia auripes (FernSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

aid), q.v., and the open, partially stored nest is left

unguarded for nearly 8 hours during the day while

the wasp hunts for prey.

All of the cockroach species found in these two nests

were reported (Krombein, 1967) from earlier nests

from the Archbold Biological Station. In addition,

Parcoblatta (?) and Cariblatta minima Hebard were

found in one or more of the earlier series of nest5.

Trypargilum collinum collinum (Smith)

FIGURES 5, 62-78

The spider-hunting wasp Trypargilum c. collinum

began nests in traps 19 (4.8-mm diameter) and 59

(6.4-mm diameter) at station 10 (Figure 5). The

station was placed 1.5 m above the ground with the

trap entrances facing south beneath the limb of a live

turkey oak. This tree was in the o|H*n sun at the edge

of a paved road through the slash pine turkey oak

association. The traps were set out 9 April and checked

periodically for nesting activity. The first evidence of

nesting was noted at 084") on the 17th, two days after

the previous check at 0800 on the 15th.

Nesting Behavior

These two nests were undoubtedly started on 16

April, because at 0845 on the 17th there was one almost completed cell in nest 59 and there were two

completed cells in 19 and two paralyzed spiders in a

partially stored third cell. There was no wasp in the

former nest, but an adult collinum, whose sex I could

not determine, flew out of nest 19 when I removed the

plain strip of wood. This wasp did not return during

the next 15 minutes. There was no further nesting

activity in either nest at 1135 and 1600, nor was the

wasp in either nest. I removed the nests at 1600 and

substituted two others of the same diameters.

At 1035 on 18 April there was a single paralyzed

araneid spider at the inner end of trap 20 at this station. The wasp was not in the nest and she had not

placed any mud at the inner end. Fifteen minutes

later a Trypargilum flew toward the nest entrance,

but was frightened by my presence and flew off. She

must have abandoned the nesting site at this time, because no additional spiders were brought in during the

next three days. Trypargilum collinum is obviously a

much more timid wasp than either of the two species

discussed earlier.
NUMBER 46 23

FIGURE 62.—Trypargilum c. collinum, cells 1 and 2, nest 19, 1630, 17 April.

Nest Architecture

A small amount of mud was plastered at the inner end

of the boring in nests 19 and 59. This mud is very

rarely omitted as in nest 20 (see also Krombein, 1967,

p. 186). Nest 59 had a single almost completed cell

14 mm long containing 14 paralyzed araneid spiders

but no wasp egg. The mud partition closing this cell

was about two-thirds complete, suggesting that the

egg might not be deposited until the partition is almost

finished. Nest 59 may have been started and abandoned by the maker of nest 19, or it may have been

that of another female which never returned during

the rest of that day.

Nest 19 had two completed cells 14 and 18 mm long

containing respectively 7 and 11 paralyzed araneid

spiders (Figure 62). There were two paralyzed araneid

spiders lying at the inner end of what would have become cell 3, but there was no mud annulus at the

outer end to delimit this cell. The mud partitions closing cells 1 and 2 were 1.5-2 mm thick.

Prey

Juvenile araneid spiders belonging to a single species

of Neoscona were used as prey in both nests. They

ranged in length from 1.5 to 4.5 mm with a mean of

3 mm. The 7 spiders stored in cell 1 of nest 19 had a

fresh weight of 50 mg and the 11 spiders in cell 2

weighed 82 mg.

Life History

The curved, sausage-shaped egg was laid obliquely on

the anterolateral portion of the abdomen of one of the
24

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURES 63-70.—Egg and larval development on first spider, cell 2, nest 19, Trypargilum c.

collinum: 63, egg, 1630, 17 April; 64, recently hatched larva, 0815, 19 April; 65, 1120, 19 April;

66, 2135, 19 April; 67, 0800, 20 April; 68, 2000, 20 April; 69, 0800, 21 April; 70, 1145, 21 April.
NUMBER 46 25

FIGURES 71-78.—Later larval development, cell 2, nest 19, Trypargilum c. collinum: 71, 1605,

21 April, 4 + hours after Figure 70; 72, 0800, 22 April; 73, 1145, 22 April; 74, 1610, 22 April;

75, 1200, 23 April; 76, 0730, 24 April; 77, 1915, 24 April, start of cocoon spinning; 78, 0800,

25 April, continuation of cocoon spinning.
26

last spiders stored in each cell (Figure 63). The eggs

were 1.9 mm long and 0.58 mm wide. The abdominal

segmentation was visible and the eggs were almost

ready to hatch at 0045 on 19 April. The larvae were

sucking fluid from the abdomen of the spider to which

each was attached by 0730 the same day. Assuming

that the eggs were laid on 16 April, as is most probable,

we can estimate that 57-63 hours elapsed between

oviposition and hatching.

The larvae continued to suck fluid from the

abdomens of the spiders for about two and a half days

(Figures 64-70). At 1400 on the 21st they were still

feeding on the abdomens of the original spiders, but

by 1600 they had transferred to other spiders and were

feeding through the abdomens of those individuals. The

growth rate now increased and during the next three

days the larvae devoured all of the spiders (Figures

71-76). They were eating the last fragments of spiders

at 1400 on 24 April and by 1915 they had begun to spin

a few silken threads to form the suspensorium for the

cocoon (Figures 77-78).

SMITHSONIAN CONTRIBUTIONS TO ZOOLOCY

The spinning of this network of white silk, in which

the cocoon proper would be suspended, required about

16 hours. Then the larvae spun the cocoon itself at

the inner end of each cell, a process which required

nearly two days. The cocoon walls were white and dry

until the larva impregnated them with liquid feces

about a day and a half after the cocoon was begun;

this impregnation turned the walls dark brown and

brittle.

The date of pupation was not determined, but a

female collinum from cell 2 left the nest on 14 June,

just 60 days after the nest was begun. The larva in

cell 1 died after spinning its cocoon.

Literatnre Cited

Krombein, K. V.

1967. Trap-Nesting Wat fit and B**i: Lift Histories, N«itt,

and Associates. Smithsonian Press, vi } 570 pages,

29 plates, 36 tablet

U.S. GOVERNMENT PRINTING OFFICE: 1970 O—371-04 9




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