saw

c o: ’1
an
o.‘
«'u

I

E

‘3"

.3

t.

a ‘1
Lu:
:35" '

(‘91 .‘
b:

N?! '
' s w,
l

a;

3 agree a? 9d. 8..
'2':
I;

but. ‘8 9.. in»: .
.....o fin“ m. . Hm” .7:
.m... . ha. 3...»... 4.x. r9

“Us ’3 5h .1»;

EL
.3. _ .z . .I
an E... pawn 3 9 .
“0!. 9 “Hal “0:6
an". A su mtg
f .... u «H 29‘.

"‘

3‘

Q.

3!

it
.;.~ 0. _ z- .
2318353 26.5

f‘

v

EEEEEEEE :EEE EEEEEEE E E E EEEEEEEE m

 

   
     

  

LIBRARY

Michigan State
University

WW

vault"

 

 

 

 

1" Irhv..'!vx.t..l ‘

,.T181‘I.i\ 1-inch ala< .

 

SEASONAL PREY 0F TRYPOXYLON BACKI SANDHOUSE

 

(HYMENOPTERA : SPHECIDAE)

By
Bruce John Wildie

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Entomology

1971

ACKNOWLEDGMENTS

I am greatly indebted to my major academic advisor, Dr. Roland
Fischer, for his guidance and patience rendered during the course of
this study.

I wish to extend my thanks to Dr. Gordon Guyer, Dr. Richard
Sauer, and Dr. T. wayne Porter for serving on my guidance committee.

I wish to extend my appreciation to Dr. Richard Sauer and
Norman Platnick for their assistance in the determination of spiders

for this study.

ii

TABLE OF CONTENTS

Page

LIST OF TABLES ,. O O O O O O O C O C O O O O O O O I O O O O O O 0 iv
LIST OF FIGURE AND GRAPH . . . . . . . . . . . . . . . . . . . . . v
INTRODUCTION 0 O O O O O O O O O O I O O O I O O O O O O O O O O O O 1
WTHODS AND TECI-INIQUES O O O O O O O O O O O O O O O O O O O I O O O 3
SEASON“. DISTRIBUTION O O O O O O O O O O O O O O O O O O O O O O 6
Linyphiidae O O O O O O O O O O O O O O O O O O O O O O O O 6
Tetragnathidae O O O O O O O O O O O O O O O O O O O O O O 8

Dietyn idae O O O O O O O O O O O O O O O O O O - I O O O O C 11
fixeridiidae O O O O O O O O O O O O O O O O O I I O O O O O O 12
Araneidae O O O O C O O O O O O O O O O O O O O O O O O O 0 l3
Erigonidae and Salticidae . . . . . . . . . . . .'. . . . . 15

DISCUSSION AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . l6

LIERATURE CITED 0 O O O O O O O I O O O O O O O O O O O O O O O O 19

iii

LIST OF TABLES

Table Page

1. Per Cent of Total Spiders Used as Prey by
Trypogylon backi by Weekly Intervals . . . . . . . . . . 9

 

2. Numbers of Spiders Used as Prey by
Trypoxy1°n baij- 0 O O O C O O O O O O O O O O O O O O O 10

iv

Figure 1.

Graph 1.

LIST OF FIGURE AND GRAPH

file S tUdy Area 0 O O O O O 0 O O O O 0

Seasonal Distribution of Spider Families

INTRODUCTION

Trypoxylon is a genus of slender, black, solitary wasps of
worldwide distribution. Currently there are 16 recognized nearctic
species. All utilize a preformed cavity (i.e., beetle burrows,
hollow twigs, straw, or other cavities of suitable diameter) in which
they build their linear nests. Spiders are used as provisions for
their nests.

Two noteworthy studies exist on the prey relationships of the
closely related Trypargilum clavatum (Say). Rau (1928) records 93
spiders distributed among 17 genera from four nests. He concludes
that the female wasp is quite adaptable in her prey selection and
that she hunted primarily in vegetation. Mums and Jeffers (1945)
record 311 spiders representing seven families for the same wasp.
They conclude that the collecting environs and prey size are the
major limiting factors affecting the provisioning habits of the wasp.
Visitation by the wasp to flowers accounted for large numbers of
Salticidae and Thomisidae.

Generally, wasps of the Genus Trypoxylon are considerably

 

smaller in size than the members of Trypargilum. Thus, prey selec-

 

tion must also be different because a Trypoxylon is simply too small

to transport many of the larger spiders utilized by Trypargilum.

 

2
Krombein (1958) recorded the linyphiid spider, Tennesselum
formicum (Emerton), from a.I.lb§gki_nest in Virginia. In 1967 he
found several nests of the same wasp in Maryland containing 5-7
spiders of the same species of ErigOnidae. Except for these isolated
instances nothing is known concerning the prey relations of this

species of Trypoxylon.

 

A rather unique situation, in which large numbers of nests of
E, begki_were available for study, has allowed me to study the prey
of this species. My objectives were to determine: 1) the groups of
spiders utilized; 2) their seasonal variation, if any; and 3) the

factors which might impinge upon the type of spider preyed upon.

METHODS AND TECHNIQUES

The study was carried out on the premises of Gull Lake Kellogg
Biological Station of Michigan State University in Kalamazoo County,

Michigan. Trypoxylon backi nests in large numbers in the hollow

 

reeds forming the windmill roof on the grounds of the Station
(Figure l). The habitat surrounding the windmill can best be described
as a "park type" habitat. The windmill is situated on the shore of
Gull Lake on a small island approximately 50 yards long and 20 yards
wide. The island is bordered on one side by Gull Lake and on the
other three sides by a narrow "lagoon". A picket fence separates the
windmill from the remainder of the island with low bushes and vines
growing along the edge of the water. The grass in the area is kept
cut for the most part but usually is not trimmed along the lake and
lagoon.

Throughout the summer 89 nests were collected from.the windmill.
These nests contained 189 cells provisioned with 5047 spiders. The
nests were marked while the wasp was in the act of provisioning, and
when completed they were taken into the laboratory. The nests were
then Opened and the spiders were counted and preserved in alcohol.
The spiders were kept separate according to nest, cell and the date

each nest was completed.

 

Figure 1.--The study area

5
The spiders were then determined as far as possible. Since
genitalia are usually needed to go to species, it was practically
impossible to determine most of the spiders beyond the generic level.

In many cases it was impossible to determine the spider beyond the

family level.

SEASONAL DISTRIBUTION

Trypoxylon backi adults are active in southern Michigan from

 

the middle of June through early September. Throughout this period
the spiders, used as prey by the wasp continue their cycle of growth
and maturation. Completion of their life cycle may not necessarily
be concomitant with the needs of the wasp for prey. Spiders which
may be utilized as prey at one period of wasp activity may be too
large, too small, or essentially nonexistent at other times during
the active season of the wasp.

Distinct differences in the spiders utilized from one part
of the season to another may be noted in Graph 1. There are wide
variations in the number of spiders of each family utilized as the
season progresses. Many of the variations can be explained by looking

at the life histories of the spider families involved.

Linyphiidae. At the beginning of the nesting season (29 June

 

through 5 duly) the linyphiids were a major source of prey, comr
prising 76 per cent of all spiders utilized during this period. This
early summer peak usage of the linyphiids rapidly dwindled at mid-
season to virtually no use as prey. At the end of August, a second

peak usage occurred at which time this group of spiders comprised

 

THERIDIIDAE

 

 

 

 

1218...!

3.:.3.-l<

33.3.01

8...! .834

 

 

 

 

'I' L

.63.»:

«1.8.3..

 

 

ERIGONI AE

 

 

 

 

 

833.:3

223.82....

9:39.05

 

o£.a3

 

Graph l.--Seasonal distribution of spider families

8
70 per cent of the prey (Table 2). A total of 1117 spiders were
determined as Linyphiidae and were represented in 71 of the 189

examined cells (Table l). A total of 13 adult Meioneta fabra

 

(Keyserling), all females except a single male, from a nest on
23 July, were used as prey from 29 June to 23 July. Six adult
females and two adult males of Bathyphantes pullatus (0. P. Cambridge)
were utilized from 29 June to 15 July.

The Linyphiidae, commonly known as the sheet-web weavers,
build their webs in a variety of situations but seem to prefer low
bushes or shrubs and may occasionally construct their webs clos; to
the ground or in leaf litter. They apparently overwinter as adults

or late instar immatures. According to Kaston (1948), Meioneta

fabra may be found at all seasons of the year. Bathyphantes concolor

 

(Wider), closely related to g, pullatus, are known to hibernate as
adults and deposit eggs in May.

All adults of both 1;. pullatus and M. _f_a_b_r_a_ were utilized
by the wasp before the end of July. Many of the 1092 undeterminable
immature linyphiids were late instar forms for both the early and
late summer peaks. Presumably, egg deposition by both species
occurred in late July or early August. The young spiderlings hatching
from these eggs were either too small to be used as prey or perhaps
were not making webs at this early stage and escaped the notice of

the wasp in this manner.

Tetragnathidae. The Linyphiidae are quickly replaced in use

 

as prey in early July by the Tetragnathidae. During the latter

 

 

N .e o N A o c m .N o o mafizofiam

o o N.m c.N w.m o.m o.HH w. maaHmz<m<

o.ow m.m~ o m. H.m H.n n.ma o.~ m¢onwHOHQ

o.H m.m m.mw m.mN o.mm o.wm m.ma o.w manHmeazoamama

N.HH o.oN o o.N N.m a.m o.mN o.eN maaHHemszHa

o N.N N.HH o.N m.N m.sa m.mN s.HH m<nHHaHmmme
.uamm N .w=< om .w:< on .wsa N sass 0N sass AH sass NH sass m
n-.ws< Hm u-.ms< «N -u.w=< on -usass NN nusass oN Insane NH unease o unease oN

 

 

mam>umunfi maxoms ma wxomn coamwOmoua mp hone mm new: mumvflmm Hauou mo usoo Homll.H mqm<H

10

TABLE 2.-—Numbers of spiders used as prey by Tropoxylon backi

 

 

No. of cells

 

in which AdUIt Immatures Total 2

represented females males of
THERIDIIDAE 67 0 555 555 11.0
LINYPHIIDAE 71 21 1092 1117 22.3
TETRAGNATHIDAE 107 0 2300 2300 45.6
DICTYNIDAE 53 80 643 724 14.3
ARANEIDAE 62 0 273 273 5.4
ERIGONIDAE 14 12 60 76 1.5

SALTICIDAE 2 O 2 2 --

 

ll
portion of July and much of August, immature spiders of the genus
Tetragnatha composed 80 per cent of the prey for T. begki. Because
of their immature state none of the 2300 specimens from 107 cells
could be identified further than genus. This genus is the most
abundant prey group of 13.222519 comprising over 45 per cent of the
total spiders used by the wasp (Table 1).

Spiders of the genus Tetragnatha, the long-jawed orbweavers,

 

build their webs in a meadow or in tall grass near water. 0f species
which are known to occur in the immediate vicinity of the nesting

site, Kaston (1948) reports that mature T, versicolor walckenaer

 

have been collected from April through September. Cocoons are made
in May, June and July. He also reports that I, straminea Emerton
matures in late May and that adults may be taken through October.

From these reports and collection data on other species of Tetragnatha,

 

it appears that they overwinter either as late instar immatures or
matures and lay their eggs in late spring or early summer. This
would account for the large number of immatures taken in July and
August by the wasps. Likewise, this also accounts for the lack of
specimens used as prey early or late in the season when adults and
late instar immatures would be the dominant portion of the spider

population. Adults and late instar immatures of the genuS'Tetragnatha

 

would undoubtedly be too large for the wasp to transport.

Dictynidae. The Dictynidae build their webs in a wide variety.

 

of places depending on the species. However, most prefer to build
above the ground using fences, walls, the tops of bushes, or a single

leaf of a plant for support of the web.

12
The Dictynidae overwinter either as adults or late instar
immatures and mature in the spring. Kaston (1948) reports that

Dictyna roscida (Hentz) overwinters in the penultimate instar or as

 

adults and that mature specimens of Dictyna brevitarsis Emerton have

 

collected from June through August.
From late June through early August, 80 mature female specimens

and a single mature male of Dictyna brevitarsis Emerton were utilized

 

as prey and were represented in 13 cells. All specimens taken early
in the season were mature and of this species, and undoubtedly, are
representatives of the overwintering pOpulation. No additional
dictynids were taken until the third week in August. It appears that
the dictynids are a minor element for prey of I. 239151 during most of
the season; however, during late August and early September, the 643
immature dictynids comprised as much as 80 per cent of the spiders
utilized by the wasp. Many of the early September dictynids were
penultimate instar individuals, and while undeterminable, they were

probably representatives of immature'23'brevitarsis, descendents of

 

the adults which were preyed upon earlier in the season.

Theridiidae. The Theridiidae, the comb-footed spiders, is a

 

large family whose members build webs of irregular meshes which may
be built in a variety of places. According to Kaston Theridion

tepidariorum (C. L. Koch) often builds its nest in the corners of

 

rooms, the angles of windows, on bridges, or on fences. Theridion
differens Emerton builds its web in grass and on low bushes and has
also been collected from cedar and pine trees. In general, bushes,

trees or buildings are preferred as sites for the Family Theridiidae.

13

Most of the species of the family Theridiidae whose biology is
known overwinter as adults or late instar immatures. According to
Bonnet (1935), individuals of Theridion tepidariorum (C. L. Koch) may
live for more than a year after reaching maturity. Theridion .
unimaculatum Emerton is an example of a species whose maturity is
attained in early spring and the adults are present throughout the
summer.

All of the 555 Theridiidae, representing 11 per cent of the
spiders collected by I, backi, were immature. The adults of this
family are undoubtedly too large to be utilized. The lack of use of
theridiids by the wasp, especially in mid and late summer, is perhaps
a reflection of the size problem because more late instar individuals

would be present late in the season.

Araneidae. 'A total of 273 immature spiders of the family
Araneidae, representing slightly over 5 per cent of all spiders, were
utilized by T. backi. Of these, 168 were immature Aranea 322., 60

were immature Araniella displicata (Hentz), 25 were Neoscona 322.,

 

and 20 others were not determinable to genus because they were far
too immature. ‘

The genera of orb weavers utilized by T. bagki are all known
to build their webs in bushes, shrubbery, and on or near structures.

According to Kaston (1948), Neoscona arabesca (Walckenaer) builds

 

its webs in tall grass or low bushes, while Neoscona benjamina

 

(walckenaer) is found in Open woods and on fences or shrubbery about

dwellings. Kaston reports that Araniella displicata builds a very

 

14
small web in tall grasses and bushes. The web is often in the space
enclosed by the bending of a single large leaf. The genus, Aranea,
has been collected from a variety of habitats, but most species prefer
to construct their webs in an arboreal habitat such as bushes or pine

trees. Many of the araneids, such as Metepeira labyrinthea (Hentz),

 

overwinter as spiderlings within the cocoon. Dondale (1961) reports

that Araneilla displicata (Hentz) appears to take more than one year

 

to mature; however, this may vary depending upon climatic conditions.
Wiehle (1931) in Germany and Nielsen (1932) in Denmark found that the

young of Aranea diadema Linnaeus emerge in May, attain their maximum

 

growth for the year in the fall, and overwinter as half-grown immatures
who reach maturity the following August. Kaston reports mature

specimens of Epeira undata (Olivier) present during the entire year.

 

Hibernation occurs during any of its stages of development. Epeira
trifolium Hentz makes its egg sacs in late September and early
October and the adults usually die before winter (Kaston 1948). The
young ordinarily emerge the following spring. It appears that,
although all stages may be present the year around, the young usually
emerge in the spring of the year.

Since most of the species, especially the genera collected
by 23.222Eiw would be too large to be utilized as adults, the early
instar immatures would be the only size group available for a prey
group by T. bagki. The araneids supplant the early summer use of
linyphiids prior to the heavy use of the tetragnathids in late July.
Apparently, the araneids fill the gap left by the maturing linyphiids

prior to the time of eclosion and general availability of immature

15
tetragnathids. They thus form a minor, but yet most important,

element in the continuance of spider predation on a seasonal basis.

Erigonidae and Salticidae. According to Kaston (1948), most

 

of the species of the Erigonidae (Micryphantidae) are found under
dead leaves near the ground, although a few of the species are arboreal.
A total of 12 female and 4 male matures and 60 immature specimens
were recovered from T. bagki_nests. This represents 1.5 per cent of
all spiders used. Since the specimens could not be determined beyond
the family level, it was impossible to ascertain whether they were
arboreal or ground inhabitants.

The Salticidae, the jumping spiders, commonly pursue their
prey rather than resort to the construction of a web for trapping
the prey. Many, however, may construct silken retreats beneath
stones or debris or in curled up leaves. Only two immature specimens
of the jumping spiders were found in 3,}bagki nests. This represented
considerably less than one per cent of the total spiders. Presumably,

their use by the wasp is only a chance occurrence.

DISCUSSION AND CONCLUSIONS

Species representing seven families of spiders were utilized
by I, baski. The prey of I, bagki do not seem to be restricted to

8a single species of spider nor to a few closely related species.

The ecological habitat occupied by the spider appears to be the most
critical factor in the selection of prey. When the various groups

of spiders are compared with respect to their habitats and habits,

it may be noted that all of the spiders are "arboreal". They live
either in the vegetation or on structures such as fences or buildings.
Also, they all form some type of web which is used to assist in
capturing their prey.

The wasp does, however, restrict its hunting habits to elevated
positions in vegetation. The fact that all of the spiders utilized
form a web could indicate that 23.222Ei searches for the web rather
than the spider. Since adult males do not construct a web as regularly
as the female, the relative inabundance of males to females (9 to 113)
would also support the last conclusion.

The fact that all of the spiders collected construct a web may
indicate that the hunting methods are similar to those reported by

Rau (1944) for Trypargilum politum (Say). He reports observing a

 

specimen of T. politum.flying into the web of a house spider, shaking

l6

l7 .
the web several times, and apparently waiting for the spider to
attack. When no response was elicited after several minutes, the
wasp flew into another web and again attempted to provoke an attack
by the spider. Although there is no direct evidence, this type of
hunting would explain the predominance of web building forms in the
prey of _'_I'_. backi.

The size of the spider preyed upon is very important in the
selection of prey and in the seasonal variation of the prey. For
this small wasp, the size of prey is the main cause of the variation
in the prey from one part of the season to the next. All of the
groups listed are present in varying numbers throughout the season;
however, the abundance of the various sizes changes throughout the
year.

Many spiders may have an initial molt within the egg sac,
followed by a second molt either in the egg sac or in the immediate
area. Dispersal thus occurs during the third instar--a stage which
may be important in the size relationship of the spider to be used
as prey. The wasp, at this time, may take advantage of the dispersal
of the spiders by returning time and again to this dispersal area for
prey. The female wasp is possibly opportunistic at such times of
initial dispersal. By taking advantage of the large numbers of small
spiders and their ready availability, the wasp decreases her hunt-
search time. This method seems to be more efficient than taking
longer periods of time in search of larger spiders in areas of
uncertainty. Some data to substantiate this premise may be noted in

two three-celled nests. In the first nest 39 of 39, 37 of 38, and

18
63 of 70 prey spiders were immature tetragnathids. Likewise, in the
second nest 61 of 63, 38 of 39, and 71 of 75 prey spiders were
tetragnathids. The total elapsed time spent provisioning her cell
with a large number of small spiders was less than the elapsed time
spent constructing her cell with fewer but larger spiders. This would
lend credence to the supposition that the wasp was obtaining her prey
with little search time in an area of high incidence--presumably the

initial dispersal period from the vicinity of the spider egg sac.

LITERATURE CITED

LITERATURE CITED

Bonnet, P. 1935. Theridion tepidariorum C. L. Koch, araignee
cosmopolite. Repartition, cycle vital, moeurs. Bull. Soc.
Nat. Hist. Toulouse 68: 335-386.

 

Dondale, C. D. 1961. Life Histories of some common spiders from
trees and shrubs in Nova Scotia. Can. Jour. Zool. 39: 777-787.

Kaston, B. J. 1948. Spiders of Connecticut. Connecticut State
Geological and Natural History Survey Bull. 70. 874 pp.

Krombein, K. V. 1958. Misc. Prey Records of solitary wasps III
(Hym.; aculeata). Proc. Biol. Soc. of Wash. 71: 21-26.

1967. Trap-nesting Wasps and Bees: Life Histories, Nests,
and Associates. Smithsonian Press: Washington, D.C. 570 pp.

Mbma, M. H. and W. F. Jeffers. 1945. Studies of the spider prey
of several mud-dauber wasps. Ann. Ent. Soc. Amer. 38: 751-753;
2 pls.

Nielsen, E. 1932. The Biology of Spiders. Copenhagen, Vol. I.
248 pp.; II. 723 pp.

Rau, P. 1928.” Field Studies in the behavior of the non-social wasps.
Trans. Acad. Sci. St. Louis 25: 325-489. 10 pls.

Wiehle, H. 1931. Neue Beitrage zur Kenntnis des Fanggewebes der

Spinnen aus den familien ArgiOpidae, Uloboridae und Theridiidae.
Ztschr. Morph. Oekol. Tiere, 20: 349-400.

19

[I
'l
I
I
I
II
I
I
III
I
I

3mm

1

I
1

WI”

68