Table Of Content2001. The Journal of Arachnology 29:267-269
SHORT COMMUNICATION
DESCRIPTION OF THE EGG SAC OF MIMETUS NOTIUS
(ARANEAE, MIMETIDAE) AND A CASE OF EGG PREDATION
BY PHALACROTOPHORA EPEIRAE (DIPTERA, PHORIDAE)
HANK GUARISCO: P.O. Box 3171, Lawrence, Kansas 66046 USA
ABSTRACT. The eggsac ofthe pirate spider, Mimetm notius, is described and compared with eggs of
other members ofthe genus. The phorid fly egg predator, Phalacrotophora epeirae, was reared from aM.
notius eggsac.
Keywords: Mimetus notius, egg sac, Phalacrotophora epeirae, predation
Members ofthefamily Mimetidaehavejus- adult females were collected from eastern red
tifiably earned the comin.on appellations of cedar (Juniperus virginiana L.) in Montgom-
“assassin” and “pirate” spiders because of ery and Greenwood counties, on 4 and 26
their interesting feeding habits. Armed with a May 1991, respectively.
series of long, slightly curved spines on the The egg sac of M. notius is fluffy, translu-
promargieal areas of the tibiae and metatarsi cent, spherical to subspherical, and is com-
mm
of legs I and II (Kastoe 1981), they enter spi^ posed of a 1 thick outer layer of sparse,
derwebs, especially those ofcomb-footed spi- curly, brown silk strands surrounding a dense
ders (Theridiidae) and orbweavers (Araeei- white central section containing the brown
dae), and prey upon the occupants (Gertsch eggs. Completely surrounding the egg sac is
&
1979). Jackson Whitehouse (1986) ob- a thin, subspherical to elliptical net of silk.
served mimetids using vibratory aggressive The egg sac is suspended within this net by
mimicry to lure spiders within striking range. several thick silk strands which extend from
Although these spiders are poorly repre- the sac to the net (Fig. 1). The shape of the
sented in systematic collections, a recent sur- net appears to be determined by the amount
vey ofthe genus Mimetus Hentz 1832 in Kan- of space available near the egg sac. Two sacs,
sas has revealed the presence of four species each laid within the confines of a petri dish,
(Guarisco & Mott 1990). Mimetus notius were surrounded by elliptical silk nets, 30 X
Chamberlin 1923 is the second most com- 23 and 50 X 20 mm in diameter. Each net was
mm
monly encountered member of the genus in 15 in height, which equalled the height
northeastern Kansas. It has been taken in of the petri dish. An egg sac discovered on
sweep samples of understory vegetation, the underside of a wooden door leaning
mostly coralberry (Symphoricarpos orbicula- against the outer wall ofa laboratory building
tus Moeech.), in woodland on the Fitch Nat- on the FNHRhad a silknetwith the following
ural History Reservation (FNHR) and on the dimensions: 30 X 30 X 7 mm. Several egg
eaves and outer walls of Reservation Head- sacs located in the comers between the eaves
quarters (FNHR) in Douglas County, Kansas. and outer walls of buildings possessed nets
The FNHR is a 590 acre (239 ha) tract ofland with similar dimensions.
which comprises all but the southwestern 50 A female collected on 4 May produced an
acres (20 ha) of Section 4 (T12S, R20E) in egg sac 7X5 mm on 16 May containing 24
Douglas County. It is located at the ecotone eggs. On 26 May, this individual produced a
between the Eastern Deciduous Forest and second egg sac (6X8 mm) containing an un-
Tallgrass Prairie Biomes, and ranges from determined number of eggs. A second female
880—1080 feet (268—329 m) in elevation obtained on 26 May produced a total of5 egg
(39°00\ 95°ir) (Fitch & Kettle 1988). Two sacs during the following fourweeks. The first
267
268 THE JOURNAL OF ARACHNOLOGY
two egg sacs were laid on 28 May and 6 June, The average number of eggs per sac = 28.9,
were 6X6 and 5X6 mm in diameter, with SD = 9.71 {n = 10).
surrounding nets 20 and 25 mm in diameter, On 3 July, I collected a M. notius egg sac
and contained a total of 29 and 37 eggs, re- from the eaves ofa house in Jefferson County,
spectively. The last three sacs were laid on 13, Kansas which contained several brown phorid
21 and 27 June and contained 21, 12, and 25 fly pupae. Two days later, an adult fly, Phal-
eggs, respectively. These sacs were laid in a acrotophora epeirae (Brues 1902)(Diptera,
small vial, and the silk nets surrounding them Phoridae), emerged from the egg sac. The re-
were 15 X 25 mm. The last two egg sacs were maining flies matured over the next few days.
probably infertile because they became cov- The structure of the egg sac of M. notius
ered with mold in a few days. resembles those of other members of the ge-
Observing the structure of egg sacs pro- nus, except for the unique net of silk which
duced in the laboratory enabled me to recog- surrounds it. Mimetus puritanus Chamberlin
nize them in the field. One egg sac discovered 1923 and M. hesperus Chamberlin 1923 both
on the FNHR on 18 June yielded 47 spider- construct spherical, bright orange, loosely wo-
lings ten days later. An egg sac collected from ven egg sacs (Guarisco & Mott 1990; Icenogle
the eaves of a building in the Topeka Zoo on 1972). Lawler (1972) described the egg sacs
21 June produced 35 spiderlings and one in- of both wild and captive M. eutypus Cham-
fertile egg on 4 July. Two egg sacs collected berlin & Ivie 1935. They were loosely woven
from the eaves of a residence in Lawrence, and those produced in captivity ranged from
Douglas County, on 13 August contained 14 white to dark rust-brown, while the wild egg
empty shells and 12 infertile eggs, and 25 sacs were all pale yellow-white. The egg sacs
empty shells and 7 infertile eggs, respectively. of Old World mimetids are generally globular
GUARISCO—EGG SAC OF MIMETUS 269
with many loops of silk on the surface and Brues, C.T. 1902. Notes onthelarvaeofsomeTex-
contain only 5-20 eggs (Heimer 1986). The an Diptera. Psyche 9:351-354.
tufted nature of the silk may protect the eggs Brues, C.T. 1903. A monograph of the North
from mechanical damage, predation, or para- American Phoridae. Transactions of the Ameri-
sitism. Although it is tempting to speculate Fitccha,nHE.nSt.om&oloWg.iDc.alKeStotclei.ety192898:.33K1a-n4s0a4s +Eco5lopig.-
upon the probable functions of the unique
ical Reserves (University of Kansas Natural Ar-
structure of the egg sac of M. notius, further eas). Transactions of the Kansas Academy of
observations are needed to explore the rela- Science 91(l-2):30-36.
tionships of various aspects of egg sac design Gertsch, W.J. 1979. American Spiders (second edi-
and relative survivability. tion). Van Nostrand Reinhold, New York. 274
The present observation on the emergence pp.
&
of Phalacrotophora epeirae from an egg sac Guarisco, H. D.J. Mott. 1990. Status of the ge-
of M. notius is the first recorded instance of nus Mimetus (Araneae: Mimetidae) in Kansas
egg predation or parasitism upon any member and a description ofthe egg sac ofMimetuspur-
of the genus Mimetus. Phalacrotophora epei- itaniis Chamberlin. Transactions of the Kansas
Academy of Science 93(3-4):79-84.
rae is a well known larval egg predator which Heimer, S. 1986. Notes of the spider family Mi-
has been reared from spider egg sacs of the metidae with description of a new genus from
following species: Linyphiidae: Pityohyphan- Australia (Arachnida, Araneae), Entomologische
tes costatus (Hentz 1850)(see Manuel 1984); Abhandlungen des Staatlichen Museums fiir
Araneidae: Larinioides Caporiacco 1934 (= Tierkunde in Dresden 49(7):113-137.
Nuctenea Simon 1864 — Epeira Walckenaer Icenogle, W.R. 1972. Notes on the biology of the
1805) sp. (see Brues 1902, 1903), Larinioides genus Mimetus. Notes on Arachnology of the
sclopetarius (Clerck 1757) (see Auten 1925), Southwest 3:19.
Jackson, R.R. & M.E.A. Whitehouse. 1986. The
Gasteracantha cancriformis (Linnaeus 1785)
(see Muma & Stone 1971); and Salticidae: biology of New Zealand and Queensland pirate
spiders (Araneae, Mimetidae): Aggressive mim-
Phidippus audax (Hentz 1845) (see Jones
icry, araneophagy and prey specialization. Jour-
1940
). nal ofZoology (London)(A) 210:279-303.
ACKNOWLEDGMENTS Jones, S.E. 1940. An annotated list of the spiders
I thank the University of Kansas Depart- of an East Central Illinois forest (Wm. Trelease
Woods, University of Illinois). Transactions of
ment of Entomology for providing laboratory the Illinois Academy of Science 33(2):216-220.
space; Paul Liechti, Kansas Biological Sur-
Kaston, B.J. 1981. Spiders ofConnecticut (revised
vey, for providing valuable equipment; Brian ed.). State Geology and Natural History Survey
V. Brown of the Natural History Museum of of Connecticut, Bulletin. No. 70. 1020 pp.
Los Angeles County, California for identifi- Lawler, N. 1972. Notes on the biology and behav-
cation of the phorid fly; and William Bell, iorofMimetus eutypus Chamberlin and Ivie (Ar-
University of Kansas for permission to collect aneae: Mimetidae). Notes on Arachnology ofthe
specimens on his property. Eor critically re- Southwest 3:7-10.
viewing the manuscript, I thank Bruce Cutler Manuel, R.L. 1984. The egg sac ofPityohyphantes
of the University of Kansas and Daniel Mott costatus (Hentz) (Araneae, Linyphiidae) and its
of Dickinson State University. I thank Will phorid parasite. Journal ofArachnology 12:371-
Bouchard ofthe University ofKansas for pro- Mu3m7a2,. M.H. & K.J. Stone. 1971. Predation o.•f
viding the art work. Voucher specimens were Gasteracantha cancriformis (Arachnidae [sic]:
deposited in the Smithsonian Collection Araneidae) eggs inFloridacitrusgrovesbyPhal-
(USNM). This paper is dedicated to the mem- acrotophora epeirae (Insecta: Phoridae) andAr-
ory of the late William Bell. achnophaga ferruginea (Insecta: Eupelmidae).
LITERATURE CITED Florida Entomologist 54(4):305--310.
Auten, M. 1925. Insects associated with spider
nests. Annals of the Entomological Society of Manuscript received 11 April 1997, revised 9
America 18:240-250. March 2001.
