Body size, duration of embryonic development, growth rate, mother-offspring interaction, and diet in Sosippus floridanus Simon (Araneae: Lycosidae)

2006·0.08 MB·English

by  Punzo, F

Bull.Br.arachnol.Soc.(2006)13(9),365–371 365
Body size, duration of embryonic development, supplies to meet their metabolic requirements
growth rate, mother–offspring interaction, and diet (Foelix,1996).Inaddition,thenewlyhatchedyoungare
in Sosippus floridanus Simon (Araneae: Lycosidae) characterised by varying degrees of gregariousness
which usually ceases after the first post-eclosion moult
Fred Punzo* (Higashi & Rovner, 1975).
In most wolf spiders (Lycosidae), a female usually
Box5F—DepartmentofBiology,
UniversityofTampa, carries her egg sac, which is attached to the spinnerets,
Tampa,Florida33606,USA under the abdomen (Rovner et al., 1973). Immediately
after hatching, spiderlings crawl up onto the dorsum of
and
their mother where they are carried about until the first
post-eclosion moult (Punzo, 2003).
Laura Haines
Sosippus floridanus Simon (Lycosidae) is one of the
P.O.Box0817,
fewmembersofagroupofsedentarylycosidsknownas
UniversityofTampa,
funnel-web spiders (subfamily Hippasinae) (Brady,
Tampa,Florida33606,USA
1962). Although they resemble vagrant wolf spiders in
retaining the egg sac-carrying habit, Hippasinae are
Summary
unique among non-burrowing, New World lycosids in
FieldandlaboratorystudieswereconductedonSosippus thattheyleadarathersedentarylifestyle.Theyconstruct
floridanus(Araneae:Lycosidae)inascrubhabitat(Hopkins funnel-shaped sheet webs that resemble those con-
Prairie)inFlorida.Inthefield,adultfemales,offspring,and structed by agelenids (Gertsch, 1979). Compared with
eggsacson20websweremonitoredduring2003.Morpho-
the more common vagrant lycosids, they exhibit a cer-
metric measurements were recorded for total body length,
taindegreeofsocialityinthatafemalesharesawebwith
lengthoffemur,patella-tibia,metatarsus,andtarsus,aswell
aslengthandwidthofthecarapaceandlabium.Sexualsize her young offspring. It should be mentioned that two
dimorphism was observed: adult females had larger total Old World lycosid subfamilies share this web-building
bodyandtarsallengths.Eggsacswereconstructedatnight trait with Hippasinae, although they construct sheet
(between 2230 and 0345h) and were carried by females
websratherthanfunnelwebs(Lehtinen&Hippa,1979).
between3Juneand23July.Numbersofspiderlingsemerg-
Webs are usually found on the ground in open, sandy
ingfromeggsacsrangedfrom22–61(mean42.8)and14–57
(mean39.2),underfieldandlaboratoryconditions,respect- habitats,orabovegroundinshrubsandcacti,withskirts
ively. Each web was characterised by a tube-like retreat of silk extending 10–30cm outward from the entrance to
extendingintoafunnel-shapedstructureatthetop,withsilk thefunnel(Brach,1976).Thefunnelretreatscanbefound
lines emanating outward for 12–40cm away from the
extendingdownwardundersurfacedebris.Femalesoften
funnel. Eight of 20 webs were constructed on the ground;
sit at the mouth of the funnel surrounded by their off-
the remaining 12 between 0.4–0.7m above the ground.
Females seized entrapped prey and carried it into the spring in numbers that can range from 20–90 (Gertsch,
retreat,followedbytheiroffspringwhichaggregatedaround 1979; Buskirk, 1981). Young may remain with their
the prey item and began feeding while it was still in the motheronthewebforupto5months(Brach,1976).
mother’sjaws.After18–21daysofage,youngwererarely This type of social interaction allows offspring to
observed in the retreat, and fed on prey at the location
remain in close proximity to their mother, where they
where it was entrapped. Sosippus floridanus fed on a wide
varietyofarthropodpreyconsistingofinsectsandspiders. are frequently observed making physical contact with
Thegestationperiodrangedfrom14–19daysforeggsunder her.Theyoungmakecontactbytouchingthelegs,palps
naturalconditions,and11–14daysunderconstantclimatic andbodyofthefemalewiththeirlegsandpalps(Punzo,
conditionsinthelaboratory.Mostspiderlingswereableto
pers. obs.). When prey is captured the female typically
emerge from the egg sac without maternal assistance.
withdraws into the retreat carrying the prey with her.
Immaturespidersshowedastrongtendencytowardmain-
tainingacloseproximitywithoneanotherwhileontheweb. The young subsequently follow her and engage in com-
munal feeding. In addition, the close proximity of
motherstotheiryoungcreatesaconditionwhereyoung
Introduction
spiders on a web are subjected to a variety of visual
Spiders are typically solitary arachnids. Out of over and chemical stimuli emanating from their mother or
30,000 known spider species, group-living behaviour siblings.
has been reported for only 30+ species (Avilés, 1997). In this study we report on various aspects of the
Depending on the species, the degree of social inter- natural history and ecology of S. floridanus, including
actioncanrangefromextendedparentalcaretolivingin body size in adults, web construction, mother–offspring
relatively permanent groups (Buskirk, 1981). The most interactions,interactionbetweenhatchlings,durationof
commonformofparentalcareinspidersisexhibitedby embryonic development (gestation period), growth rate,
those species in which the mother lacerates the egg sac, and diet composition.
enabling the spiderlings to emerge, and/or passively or
actively guards her spiderlings for a period of time that
typically ranges from a few days to over a week Material and methods
(D’Andrea, 1987). Typically, spiderlings do not capture
Field studies and general description of study area
prey during this period and utilise remaining yolk
Sosippus floridanus was studied at Hopkins Prairie,
*Towhomcorrespondenceshouldbeaddressed. an inland scrub habitat (Big Scrub) within the Ocala
366 DevelopmentandbehaviourofSosippusfloridanus
National Forest, located just off State Road 314, 15km andfemaleswerecomparedusingastudentt-test(Sokal
north-east of Silver Springs, Florida (Marion County). & Rohlf, 1995).
It is best characterised as Florida scrub habitat, with Webs in the field were also monitored carefully after
well-drainedsandy,siliceousentisolsoilsthatareamong females deposited egg sacs, and the number of days
thedriestandleastfertilesoilsinFlorida(Myers,1990). between deposition and emergence of spiderlings was
Dominant shrub and tree layer species include saw recorded for 12 egg sacs.
palmetto (Serenoa repens), sand pine (Pinus clausa), live
oak (Quercus geminata), scrub oak (Q. inopona), rusty
lyonia (Lyonia ferruginea), dwarf palm (Sabal etonia), Growth rate in the field
and Florida rosemary (Ceratiola ericoides). Dominant
Ten immature spiders from each of five additional
ground cover vegetation includes beak rush (Rhyncho-
webs were monitored at random approximately once
spora megalocarpa), milk peas (Galactia spp.), gopher
every 3 weeks, between 9 June and 18 July, in order to
apple(Licaniamichauxii)andlichens(Cladonialeporina,
determine rate of growth. Between 1 January and
C. prostrata and Cladina evansii). The ground contains
31 December, spiders were also collected using pitfall
areas with pronounced layers of litter, and scattered
traps. Traps consisted of 300-ml plastic containers
clumpsofvegetationinterspersedwithpatchesofbarren
placed into the ground with the lip of the container at
sand.
ground level. Five rectangular grids (30(cid:1)20m), separ-
Seventy-two webs containing adult females with their
atedbyaminimumdistanceof50m,wereestablishedat
egg sacs or young were monitored every other day
thestudyarea.Trapsweresetalonglinearaxes,30min
betweenthemonthsofMarchthroughSeptember2003.
length, using a yellow rope laid on the ground. Each
Only data obtained from webs in which the female
lineararrayoftrapswasseparatedbyadistanceof4m,
survived until the young left the web (n=20) were used
and traps were set at intervals of 5m. Each trap
for analyses on field data. The positions of the female
contained about 4cm of a 50/50 mixture of ethylene
andyoungwithinthefunnelwebwerealsorecorded.In
glycolandwater.Trapswerecheckedonaweeklybasis,
order to determine diet composition, undigested prey
and the number of individuals/month (for immatures,
within these 20 webs were identified on a weekly basis,
adultmalesandfemales)overthecourseoftheyearwas
between 1 June and 1 August (8 sample periods). Prey
recorded.DifferenceswerecomparedusingaChi-square
itemswereremovedfromthewebscarefullywiththeaid
test (Sokal & Rohlf, 1995).
of iris microdissection scissors and forceps, placed in
For immature spiders on webs, measurement of
70% ethanol, and returned to the laboratory for subse-
carapace width began within 36h after the day (day 4)
quent identification to order, superfamily, or family,
whentheyhadlefttheirmother’sbackandcrawledonto
depending on state of digestion.
the web. Spiders were coaxed off the web with a fine
camel-hairbrush,measured,andplacedinvialscontain-
ing 70% ethanol. Similar measurements were taken for
Morphometric data
pitfall-trap specimens, with a dissecting microscope
to the nearest 0.1mm using an ocular micrometer.
The following measurements were recorded for each
Carapace width has been shown to be a reliable estima-
adultfemale(>18mm,n=20)locatedonaweb,andfor
tor of post-embryonic developmental rate in spiders
males (>12mm, n=100) collected in the same area
(Hagstrum, 1971). Means were compared using an
using pitfall traps (Model 2838A, BioQuip, Gardena,
analysis of variance (ANOVA) with a Bonferroni-
California): (1) total body length (TBL); (2) carapace
adjusted alpha level of p=0.05 (Sokal & Rohlf, 1995).
length (CL); (3) carapace width (CW); (4) length (LL)
and (5) width (LW) of labium; (6) femur length (FmL);
(7) patella-tibia length (Pt-TbL); (8) metatarsus length
Laboratory housing conditions and experiments
(MtL); and (9) tarsus length (TsL). To take measure-
ments,femalesweregentlyeasedofftheirwebwithafine Twenty males, and 15 females which had not yet
camel-hair brush, and males were removed from pitfall deposited egg sacs, were collected from the field and
traps with a flattened wooden tongue depressor. The broughtbacktothelaboratory.Malesandfemaleswere
spiders were then placed individually in Drosophila placedindividuallyin10-lglassaquaria(holdingcages).
vials (Carolina Biological Supply, Burlington, North The floor of each aquarium was covered with vermicu-
Carolina). Each vial opening was fitted with a cork lite to a depth of 4cm. Several artificial plants were
stopperwhichhadacentrally-locatedglasstubethrough placed in each aquarium to add structural complexity
which carbon dioxide could be introduced into the vial to the habitat and to facilitate web construction. All
from a portable CO cylinder. Spiders were anaesthe- females constructed funnel webs within their holding
2
tised with CO , and measurements were taken using a cages within 24 to 72h. Aquaria were housed in a
2
UnitronModel440dissectionmicroscope(BocaRaton, climate-controlled room (25(cid:2)0.2(C; 70–75% RH;
Florida) fitted with an ocular micrometer. All measure- 12L:12D photoperiod regime).
mentswererecordedbetween15–18July.Aftermeasure- All spiders were fed on a mixed diet of adult crickets
ments were taken, females were allowed to recover fully (Acheta spp.), cockroaches (Periplaneta americana) and
andreturnedtotheirwebs.Maleswereheldincaptivity fruitflies(Drosophilavirilis).Preywereplacedontheweb
for future studies. Differences between means for males for females, and on the aquarium floor for males.
F.Punzo&LauraHaines 367
Gestation period Parameter Males Females
Experiments were conducted to compare the rate of TBL 12.81(2.12)a 18.2 (1.21)b
CL 6.23(0.54)a 6.61(1.01)a
embryonicdevelopmentforeggsacsexposedtonatural,
CW 4.48(0.35)a 4.91(0.42)a
fluctuating conditions of temperature, RH and photo-
LL 0.88(0.13)a 0.94(0.14)a
period in the field, with egg sacs maintained under LW 0.79(0.07)a 0.88(0.11)a
controlled laboratory conditions. Fourteen egg sacs FmL 6.24(0.73)a 5.83(0.37)a
were placed individually in plastic Drosophila vials Pt-TbL 7.22(0.62)a 6.78(0.44)a
immediately after being constructed by females, and MtL 6.56(1.11)a 5.92(1.01)a
TsL 3.94(0.43)a 2.69(0.26)b
maintained under identical climatic conditions to those
describedaboveinaPercivalModel85Aenvironmental
Table1: Morphometric data for adult males (n=100) and females
chamber (Boone, Iowa). The number of days between (n=20) of Sosippus floridanus. TBL=total body length;
time of deposition and emergence of spiderlings was CL=carapace length; CW=carapace width; LL=labium
recorded for each egg sac from which spiderlings were length; LW=labium width; FmL=femur length; Pt-
TbL=patella-tibia length; MtL=metatarsus length;
observed to emerge (n=10).
TsL=tarsuslength.Allmeasurementsexpressedinmmfor
spiders measured between 15–18 July, in Marion County,
Florida. Data expressed as means ((cid:2)SE). Values in rows
Maternal–younginteractionandemergenceofyoungfrom followed by a different letter are significantly different
egg sac (t-test,p<0.05).
Experiments were conducted to determine if young
could emerge from egg sacs without assistance from
their mother. Thirty unbreached egg sacs were placed
individually in glass vials (50mm in height; 30cm in
Standard Time). They were carried by females in webs
diameter) and capped with perforated plastic stoppers.
between3Juneand23July,andbetween18Juneand16
Egg sacs were observed on a daily basis to see whether
July, under field and laboratory conditions, respectively
or not young would emerge.
(Table 2). The gestation period ranged from 14–19 days
To determine whether or not interaction of the (mean 16.9(cid:2)1.73SE) for eggs in the field, and from
mother with her offspring was important for their sur- 11–14 days (mean 12.8(cid:2)0.82) under laboratory con-
vival, 20 pairs of unrelated middle-instar spiders were ditions. This difference between means was significant
placed at opposite ends of 100mm glass petri dishes
(t=12.96, p<0.05).
containing no web material, one pair/dish. After 15min
The number of spiderlings emerging from egg sacs
their position within the dish was recorded. Recording ranged from 22–61 (mean 42.8(cid:2)6.85SE), and 14–57
was repeated at hourly intervals for 4h, and then after (39.2(cid:2)5.88), under field and laboratory conditions,
24h, 2 days, and 3 days. Distances separating the
respectively (Table 2). These means were not signifi-
spiders within each dish were modified from those cantly different (p>0.05). Emerging spiderlings, in the
proposed by Downes (1994) in his study on the social
field and in captivity, climbed onto the dorsum of the
spiderPhryganoporuscandidus(L.Koch)(Desidae),and
mother’s abdomen and remained there until their first
defined as follows: (1) in physical contact with one
moult, a period of 3–4 days.
another (touching); (2) close (<10mm apart); (3) inter-
mediate(16to40mmapart);(4)far(41to55mm);and
(5) distant (>55mm). These distances were based on
Fieldconditions Laboratoryconditions
over80hofobservationofyoungonwebsinthefield.A
Eggsac N DD DE Eggsac N DD DE
Chi-square test was used to test for differences between
1 37 21June 07July 1 46 24June 05July
the frequency distributions of various time intervals
2 54 23June 09July 2 31 21June 04July
(Sokal & Rohlf, 1995).
3 48 25June 11July 3 49 28June 10July
4 51 13June 29June 4 23 19June 02July
5 29 16June 03July 5 55 26June 08July
Results 6 44 12June 27June 6 38 22June 02July
7 22 03June 19June 7 14 18June 29June
Morphometric data 8 61 22June 05July 8 37 04July 16July
9 34 05July 23July 9 57 01July 14July
The results for various measurements for males and
10 47 06July 22July 10 42 27June 08July
females are listed in Table 1. Significant differences 11 35 24June 10July
between the sexes (sexual dimorphism) were found only 12 52 26June 12July
for total body length (t=10.87, p<0.05) and tarsus MGP 16.9((cid:2)1.73SE) 12.8((cid:2)0.82)
length (t=14.26, p<0.05).
Table2: Numbers of hatchling spiderlings that emerged from egg
sacs deposited by females under laboratory conditions
(25(cid:2)0.2(C;70–75%RH;12L:12Dphotoperiodregime)as
Eggsacconstruction,numberofemergingspiderlings,and
well as for eggs that hatched under field conditions. Data
gestation period from 2003. N=number of emerging spiderlings; DD=date
egg sac was deposited; DE=date spiderlings emerged;
Alleggsacswereconstructedatnight,between3June MGP=meangestationperiod(indays);differencebetween
and 6 July, and between 2230 and 0345h (Eastern laboratoryandfielddatawassignificant(p<0.05).
368 DevelopmentandbehaviourofSosippusfloridanus
Construction of webs in the field Preycapture,dietcomposition,andlocationoffemaleand
spiderlings
Webswereconstructedeitherontheground(n=8)or
from0.4–0.7mabovetheground(n=12).Groundwebs During early morning hours (0730–0930) females were
occurred on the ground in sandy areas (n=5) or in usually observed resting at the mouth of the funnel
clumps of decaying cactus (Opuntia) plants (n=3), and retreat. If young were present they typically positioned
werecharacterisedbyatube-likesilkenretreatextending themselves in a circle or semicircle around her body.
into a funnel-shaped structure at the top, with emanat- Between0930and1500h,femalesmovedbackandforth
ing silk lines extending outward for 12–40cm. Webs betweentheouterboundariesofthewebandthemouthof
built above the ground were located within fronds of the retreat. The young usually left the web and dispersed
saw palmetto. whentheywere75–90daysold(>1.0cminlength).
Prey N NW Prey N NW
Insecta Ichneumonidae(A) 5 5
Coleoptera(A) Chalcididae(A) 12 10
Brachypteridae 4 3 Chrysididae(A) 2 2
Carabidae 9 7 Cynipidae(A) 1 1
Elateridae 5 5 Unidentified(A) 9 6
Lampyridae 22 20 Formicoidea(ants)
Lycidae 3 3 Formicidae(A) 19 13
Scarabaeidae 4 4 Apoidea(bees)
Unidentified 11 9 Apidae(A) 5 5
Dictyoptera Colletidae(A) 3 3
Blattaria(cockroaches)(N) 10 7 Halictidae(A) 5 3
Mantoidea(mantids)(N) 4 4 Isoptera(termites)(A) 28 17
Diptera(A) Lepidoptera
Agromyzidae 5 5 Heterocera(moths)
Asilidae 2 2 Geometridae(A) 1 1
Calliphoridae 7 6 Unidentified(A) 3 2
Culicidae(mosquitos) 32 20 (L) 3 3
Drosophilidae(vinegarflies) 29 18 Rhopalocera(butterflies)
Muscidae 12 10 Hesperiidae(A) 2 2
Syrphidae 10 8 Lycaenidae(A) 3 2
Tabanidae 14 8 Nymphalidae(A) 5 5
Tephritidae(fruitflies) 22 15 2 2
Tipulidae 4 3 Pieridae(A) 11 9
Unidentified 12 9 Satyridae(A) 2 2
Ephemeroptera(A) Neuroptera
Baetidae 13 11 Chrysopidae(A) 21 14
Heptageniidae 9 5 Unidentified(A) 7 5
Ephemeridae 6 6 Odonata
Hemiptera Calopterygidae(A) 3 3
Coreidae(A) 2 2 Coenagrionidae(A) 1 1
(N) 4 4 Lestidae(A) 1 1
Lygaeidae(A) 14 10 Orthoptera
(N) 2 2 Acrididae(grasshoppers)(N) 7 6
Miridae(A) 11 10 Gryllacrididae(leaf-rollingcrickets)(N) 4 4
Unidentified(A) 8 7 Gryllidae(crickets)(N) 8 5
(N) 7 4 Tettigoniidae(A) 2 2
Homoptera (N) 4 3
Aleyrodidae(whiteflies)(A) 25 16 Unidentified(N) 7 5
Achilidae(A) 2 2 Thysanoptera(A) 8 7
(N) 3 3 Arachnida
Cicadellidae(A) 10 8 Araneae
Cicadidae(A) 2 2 Araneidae(A) 12 10
Fulgoridae(A) 10 7 Gnaphosidae(A) 2 2
(N) 5 3 Lycosidae(A) 4 4
Membracidae(A) 11 9 (I) 3 3
Unidentified(A) 9 9 Unidentified(A) 7 7
Hymenoptera (I) 7 4
Symphyta(wasps) Opiliones(A) 3 3
Bethylidae(A) 2 2 Unidentified(A) 2 2
Braconidae(A) 5 4 (I) 4 4
Table3: Totalnumbers(N)ofpreyitemsidentifiedfromwebsofSosippusfloridanusundernaturalconditions.Datacompiledweeklyfrom20webs
from1Juneto1August(8sampleperiods).LifecyclestageofpreydesignatedasA(adult),N(nymph),L(larva),orI(immature).The
numberofwebs(outof20)containingaparticularpreyitemasdesignatedasNW.
F.Punzo&LauraHaines 369
Immatures Adults flies (Drosophilidae), white flies (Aleyrodidae), alate
09June 30June 18July 06August 25August 16September termites (Isoptera), and lacewings (Chrysopidae). Half
_ \ _ \
of the webs contained araneid spiders, chalcid wasps,
n=41 n=62 n=55 n=38 n=29 n=64 n=34 n=57
lygaeidandmiridbugs,baetidmayflies,andmuscidflies.
1.66a 1.78a 2.91b 3.39b 4.46c 4.68c 4.44c 4.69c
(0.19) (0.25) (0.36) (0.38) (0.42) (0.28) (0.48) (0.38)
Phenology
Table4: Carapacewidths(inmm)forspiderssampledfromfivewebs With the exception of December and January,
(10spiders/web)aswellaspitfalltrapsoverthecourseofa
immature spiders were found throughout the year and
reproductive season. Data expressed as means ((cid:2)SE).
Valuesinrowsfollowedbydifferentlettersaresignificantly were significantly more abundant than adults (Fig. 1;
different (ANOVA, with Bonferroni-adjusted alpha level, (cid:1)2=27.81, p<0.01). Spiderlings that hatch in August
p<0.05). overwinterasimmatures,findingshelterunderleaflitter,
rocks, and other ground surface debris, in shallow
Typically,whenpreywereobservedbeingensnaredin ground holes, and within bark crevices. Males and
webs, the female moved quickly from the mouth of the females that hatched earlier in the year were found
funnel to the struggling prey. She then seized it and overwinteringasadults.Therewerenosignificantdiffer-
usually brought it back into the retreat. Early-instar ences between the numbers of adult males and females
spiderlings,between4–18daysold,usuallywaitedinthe throughout the sampling period ((cid:1)2=2.07, p>0.05).
retreat,wherefoodwascarriedtothembytheirmother.
The young then aggregated around the prey item
Growth rate
secured in the mother’s jaws and began to feed. After
18–21 days, the young were rarely observed within the Mean body sizes under natural conditions, for imma-
retreat and they fed on prey at the location within the ture stages of both sexes as well as adult males and
web where the prey was entrapped, without assistance females at various sampling periods, are listed in
from their mother. Table 4. There was an overall significant effect of time
The prey items found in the webs of S. floridanus are (date) on body size (F=28.12, p<0.05). Immatures had
listed in Table 3. This list indicates that S. floridanus attained a significantly larger size by 18 July, as com-
feeds on a wide variety of insects and arachnids. Insects pared with spiders measured on 9 June and 30 June.
andspiderscapturedbyS.floridanusincludespeciesthat Another significant increase in size was achieved by
spend a significant amount of time on the ground, adult males and females by 25 August.
including beetles (Coleoptera), cockroaches (Blattaria),
ants (Formicidae), and crickets (Gryllidae and
Maternal–younginteractionandemergenceofyoungfrom
Gryllacrididae), as well as those commonly found
egg sac
crawling up on shrubs such as fireflies (Lampyridae),
mantids (Mantoidea), hemipterans (plant bugs), hom- In 4 out of 30 unbreached egg sacs, without the
opterans, caterpillars (Lepidoptera), and orthopterans presence of a maternal parent to provide assistance,
(grasshoppersandkatydids).Inaddition,manykindsof spiderlings failed to emerge and starved. Successful
aerialinsectsarecapturedincludingflies(Diptera),alate emergencewasobservedintheother26eggsacs.Spiders
termites (Isoptera), moths and butterflies, mayflies spent most of their time in physical contact or close
(Ephemeroptera),lacewings(Neuroptera),andbeesand proximity (Table 5). The percentage of time spent in
wasps (Hymenoptera). closeproximityincreasedfrom25–35%overthefirst2h
Thirteen to 20 (65–100%) of the webs examined of observation, to 55–60% at the 2 and 3-day intervals,
contained ants (Formicidae), fireflies (Lampyridae), respectively. As time progressed fewer spiders were seen
mosquitos (Culicidae), fruitflies (Tephritidae), vinegar at the furthest distances (far and distant). At 24h only
Timeinterval Touching Close Intermediate Far Distant
15min 6(30) 7(35) 3(15) 1(5) 3(15)
1h 5(25) 5(25) 4(20) 4(20) 2(10)
2h 7(35) 7(35) 4(20) 1(5) 1(5)
3h 8(40) 9(45) 1(5) 1(5) 1(5)
4h 7(35) 12(60) 1(5) 0(0) 0(0)
1day 6(30) 13(65) 0(0) 1(5) 0(0)
2days 7(35) 11(55) 2(10) 0(0) 0(0)
3days 6(30) 12(60) 2(10) 0(0) 0(0)
Table5: Distancesmaintainedbetween20pairsofmiddle-instarSosippusfloridanus.Spiderswereplaced
in pairs in 100-mm petri dishes and the distance between them recorded at various time
intervals.Distancesdefinedas:touching(inphysicalcontact);close(<10mmapart);intermedi-
ate (16–40mm apart); far (41–55mm); distant (>55mm). Observations were recorded at
15min after the spiders were initially placed in the petri dish, and at various time intervals
afterwards. Data expressed as number of pairs followed by the percentage of 20 pairs (in
parentheses)showingvariousdegreesofproximity.
370 DevelopmentandbehaviourofSosippusfloridanus
predator like other web-building spiders. In addition,
althoughwebswereneverfoundmorethan0.7mabove
the ground, many aerial insects including flies, mayflies,
damselflies, white flies, wasps, bees, moths and butter-
flies, and lacewings were trapped, as well as arthropods
that move over the ground surface (ants, beetles, cock-
roaches, spiders) or crawl up into shrubs or trees
(hemipterans,homopterans,orthopterans,arachnids).It
is interesting to note that although present at this study
site, walking stick insects (Phasmatodea), stink bugs
(Pentatomidae), ladybird beetles (Coccinellidae), blister
beetles(Meloidae),andvelvetants(Mutillidae)werenot
identified from any of the webs. Pentatomids, meloids,
coccinellids, and mutillids are well known for their
Fig. 1: Total numbers of immature and adult Sosippus floridanus chemical defence. Perhaps, if these insects are caught,
collected in pitfall traps set in a scrub habitat at Hopkins theyarenotattackedbyS.floridanuswhich,unlikesome
Prairie, Florida, over the course of a year. Squares= orb-weavers, is not capable of wrapping the prey in a
immatures;circles=adultmales;triangles=adultfemales.
thicksilkcoveringtominimisetherepellantchemicalsor
stinging defences. If entrapped, these insects may be
removedfromthewebinstead.Phasmatidsaregenerally
onepairwereseparatedbyadistanceof41–55mm.The palatable, and so their absence cannot be explained.
frequencydistributionsfordistancecategoriesatthe1-h Although females did not lacerate the egg sac, as has
and 3-day time intervals were significantly different beenreportedinotherspeciesoflycosids(Foelix,1996),
((cid:1)2=13.85, p<0.01). spiderlings emerged successfully from 87% of egg sacs
without any maternal assistance. Females did not
actively feed their young. There was no evidence of
Discussion
femalesseekingtoshareorregurgitatingfood.Preythat
Sosippus floridanus was a common element of the hadbeenentrappedinthewebwereseizedbythefemale
spiderfaunaoftheHopkinsPrairieinlandscrubhabitat. and dragged into the retreat. Young spiders (4–18 days
Although immatures were found from February to old)followedtheirmotherintotheretreatandfedupon
November, their peak period of occurrence was from the prey while it was in the female’s chelicerae. Females
MaythroughAugust.Theearliestthatadultmaleswere typicallyfedwiththeiryounguntilonlytheoutercuticle
collected was in March, and they were most abundant of the prey remained. In some cases, the young contin-
from May through August. Adult females were not ued to feed upon what remained of the macerated prey
collected until early April, and their period of peak after it had been dropped by the female. Frequently, in
abundance was similar to that of males. In addition, these communal feeding bouts, the digestive juices and
bodysizesincreasedsignificantlybymid-July,andagain partially-digested prey surrounded the prey item, form-
by late August. ing a somewhat continuous mixture from which all of
The length of the gestation period was significantly the spiders fed.
reduced for eggs housed in the laboratory compared After 18–21 days of age, immatures seldom entered
with those in the field. This may be attributed to the thewebretreatbutfedonpreyatthosesiteswhereprey
controlledenvironmentalconditionsoftemperatureand became entrapped. Typically, those individuals closest
relative humidity in the laboratory. Naturally-occurring to the prey would attack first. This is in agreement with
fluctuations in temperature and RH have been reported a previous study by Downes (1994) on the social spider
to affect the rate of embryonic development in a variety Phryganoporus candidus, which showed that out of 20
of terrestrial arthropods, including insects (May, immaturespiderstomakefirstcontactwithapreyitem,
1985; Punzo, 2000), centipedes and millipedes 85%wereamongthosenearesttoit.Similarresultshave
(Cloudsley-Thompson, 1961), solifugids (Punzo, 1998) been reported for other social spiders including
and other species of spiders (Pulz, 1987). Anelosimus eximius (Keyserling) (Brach, 1975) and
The fact that webs were constructed both on and off StegodyphusmimosarumPavesi(Crouch&Lubin,2000).
thegroundsuggeststhatwebplacementmaydependon Growth rate as measured by carapace width showed
specific features of the microhabitat, including soil type an increase as the reproductive season progressed, from
and vegetation structure, as well as availability of suit- earlyJunetolateAugust.Immaturesshowednosignifi-
able sites that are not already occupied by other web- cant change during June, but there was a significant
building spiders. These general features of the increase in size by 18 July, and again by 25 August,
environment have been known to affect microhabitat when most spiders attained adult size.
selection in many terrestrial arthropods (Polis, 1991; Immatures and adults were active at the ground
Punzo, 2000) as well as web site location in araneid surface in all months except December and January.
spiders (Wise, 1993). Peak abundance for all life cycle stages was observed
ThepreyitemscollectedfromthewebsofS.floridanus from May through August. This corresponds to peak
in the field indicate that this spider is a generalist periods of abundance reported for other species of
F.Punzo&LauraHaines 371
vagrant lycosids in the south-eastern United States CROUCH, T. E. & LUBIN, Y. 2000: Effects of climate and prey
(Kuenzler, 1958; Draney, 1997). availability on foraging in a social spider, Stegodyphus
mimosarum(Araneae:Eresidae).J.Arachnol.28:158–168.
Immature spiders showed a tendency to stay in close
D’ANDREA, M. 1987: Social behaviour in spiders (Arachnida,
proximity with their siblings in laboratory tests. This Araneae).Monitorezool.ital.(N.S.Monogr.)3:1–156.
may be influenced by chemical cues associated with the DOWNES,M.F.1994:Tolerance,interattractionandco-operationin
integument or that occur on the silk. Spiders in close the behaviour of the social spider Phryganoporus candidus
proximity can respond in greater numbers to entrapped (Araneae:Desidae).Bull.Br.arachnol.Soc.9:309–317.
DRANEY, M. 1997: Ground-layer spiders (Araneae) of a Georgia
prey, thereby facilitating transfer of nutrients more
piedmont floodplain agroecosystem: species list, phenology,
rapidly to a greater number of individuals. It has been andhabitatselection.J.Arachnol.25:333–351.
shown that one advantage of sociality in species of FOELIX, R. F. 1996: Biology of spiders. Oxford University Press,
spiders with more elaborate social interactions is that it Oxford.
enables them to capture larger prey (Nentwig, 1985). GERTSCH, W. J. 1979: American spiders (2nd ed.). Van Nostrand,
NewYork.
This, in turn, provides them with greater caloric intake
HAGSTRUM,D.1971:Carapacewidthasatoolforevaluatingthe
per capture. Future studies on S. floridanus should
rateofdevelopmentofspidersinthelaboratoryandfield.Ann.
attempttoassesstherangeinsizeofpreycaptured,and ent.Soc.Am.64:757–760.
whether this is in any way associated with survivorship, HIGASHI,G.A.&ROVNER,J.S.1975:Post-emergencebehaviour
growth rate and fecundity. ofjuvenilelycosidspiders.Bull.Br.arachnol.Soc.3:113–119.
KUENZLER, E. J. 1958: Niche relations of three species of lycosid
spiders.Ecology39:494–500.
Acknowledgements LEHTINEN, P. T. & HIPPA, H. 1979: Spiders of the Oriental-
Australian region. I. Lycosidae: Vaconiinae and Zoicinae.
We thank P. Merrett, M. DeCosta, and anonymous Annlszool.fenn.16:1–22.
reviewers for comments on an earlier draft of the MAY, M. L. 1985: Thermoregulation. In G. A. Kerkut & I.
Gilbert(eds.),Comparativeinsectphysiology,biochemistryand
manuscript, B. Garman for consultation and statistical
pharmacology5:507–552.PergamonPress,NewYork.
analyses, and T. Howland, C. Farmer, T. Rich and J.
MYERS,R.L.1990:Scrubandhighpine.InR.L.MyersandJ.J.
Bottrell for assistance in field and laboratory observa- Ewel(eds.),EcosystemsofFlorida:150–193.UniversityPresses
tions. This research was supported by a Faculty ofFlorida,Gainesville,Florida.
Development Grant to FP from the University of NENTWIG, W. 1985: Social spiders catch larger prey: a study of
Anelosimus eximius (Araneae: Theridiidae). Behav. Ecol.
Tampa.
Sociobiol.17:79–85.
POLIS,G.A.1991:Theecologyofdesertcommunities.Universityof
References ArizonaPress,Tucson,Arizona.
PULZ, R. 1987: Thermal and water relations. In W. Nentwig (ed.),
AVILÉS, 1997: Causes and consequences of cooperation and Ecophysiologyofspiders:26–55.Springer,Heidelberg.
permanent sociality in spiders. In J. C. Choe & B. J. Crespi PUNZO,F.1998:Thebiologyofcamel-spiders(Arachnida,Solifugae).
(eds.),Theevolutionofsocialbehaviourininsectsandarachnids: KluwerAcademicPublishers,Norwell,Massachusetts.
476–499.CambridgeUniversityPress,Cambridge. PUNZO,F.2000:Desertarthropods:lifehistoryvariations.Springer,
BRACH, V. 1975: The biology of Anelosimus eximius (Araneae: Heidelberg.
Theridiidae).Bull.Sth.Calif.Acad.Sci.74:37–41. PUNZO,F.2003:Observationsonthenaturalhistoryandecologyof
BRACH, V. 1976: Subsocial behavior in the funnel-web wolf spider the wolf spider Hogna carolinensis Walckenaer (Araneae:
Sosippus floridanus (Araneae: Lycosidae). Fla Scient. 59: Lycosidae) in the northern Chihuahuan Desert. Bull. Br.
225–229. arachnol.Soc.12:399–405.
BRADY, A. R. 1962: The spider genus Sosippus in North America, ROVNER,J.S.,HIGASHI,G.A.&FOELIX,R.F.1973:Maternal
Mexico, and Central America (Araneae: Lycosidae). Psyche, behaviorinwolfspiders:theroleofabdominalhairs.Science,
Camb.69:129–163. N.Y.182:1153–1154.
BUSKIRK,R.E.1981:SocialityintheArachnida.InH.R.Hermann SOKAL, R. R. & ROHLF, B. J. 1995: Biometry (2nd ed.). W. H.
(ed.),Socialinsects2:282–367.AcademicPress,NewYork. Freeman,NewYork.
CLOUDSLEY-THOMPSON, J. L. 1991: Ecophysiology of desert WISE,D.H.1993:Spidersinecologicalwebs.CambridgeUniversity
arthropodsandreptiles.Springer,Heidelberg. Press,Cambridge.