Dispersal and Survivorship in a Population of Geolycosa Turricola (Araneae, Lycosidae)

6 Pages·1991·3.9 MB·English

by  Patricia R Miller

)
1991. TheJournal ofArachnology 19:49-54
DISPERSAL AND SURVIVORSHIP IN A POPULATION OF
GEOLYCOSA TURRICOLA (ARANEAE, LYCOSIDAE)
Patricia R. Miller:' Department of Entomology, Mississippi Entomological Museum,
Mississippi State University, Mississippi State, Mississippi 39762 USA
GaryL. Miller: Department ofBiology, The University ofMississippi, University, Mis-
sissippi 38677 USA
Abstract. A population ofthe burrowingwolfspider Geolycosa turricola in Mississippi
was monitored over a period of4 years. Weekly censuses ofthe number ofburrows that
were active, open but not active, or inactive were taken. The timing ofthe dispersal of
spiderlingswasexaminedbyuseofcagingexperiments. Ahabitatmanipulationexperiment
was used to assess burrow site preferences. This population reproduced on a 2-yearcycle;
noyoungwereproducedinevenyears. Theresultssuggestthatsomedispersingspiderlings
constructburrowsimmediatelyafterleavingtheirmother’sburrowwhileothersoverwinter
andbuildtheirfirstburrowduringthespring. Two dispersinggroupsare identifiedandare
shown to have different survivorship properties. The importance ofthis dispersal strategy
in terms ofsubsocial behavioris discussed.
A number of field studies of the population a 1 ha Selma Chalkdeposit (Harper 1857; Miller
dynamicsofthe obligate burrowingwolfspiders 1984b)surroundedonthreesidesbythickgrowths
{Geolycosa)havebeenundertakeninrecentyears ofsouthern red cedar {Juniperus silicicola) and
(e.g., McQueen 1978, 1983; Conley 1985). For ontheothersidebyadirtroad.Thepredominant
the most part these studies have confirmed the vegetation, beard grass (Andropogon sp.), oc-
incidental observations ofWallace (1942): mul- curredinlargeclumpsinterspersedwithbareand
tiyear life cycles predominate (McQueen 1978), litter-covered ground.
dispersalofyoungfromthematernalburrowoc- A number ofsmall isolated populations ofG.
cursintheearlysummer(McQueen 1978, 1983; turricola occurred in similar habitats within a 6
Conley 1985) and may be by ballooning (Miller km radius ofthe study population. These pop-
1984a; McQueen 1978), and mortality of spi- ulations were monitored periodically to deter-
derlings is high (Humphreys 1976; McQueen mine the extent ofinterpopulation variation in
1978). However, severalquestionsregardingthe the timing ofreproduction and dispersal.
populationdynamicsofthesespidersremainun- In the fall of 1982 and early spring of 1983,
answered. Chiefamong these are questions re- prior to the onset ofthe dispersal ofyoung, all
latingtothetimingofinitialburrowconstruction burrowsinthefieldweremarkedwithnumbered
in relation to the onset ofdispersal, burrow site surveyor’s flags. Beginningin the springof 1983
preferenceand tenacity, andthe extentto which the population was censused at approximately
the timing ofdispersal and the size ofthe dis- weekly intervalsbetween March and Octoberof
persing spider affects survivorship. Here we ad- each year and once a month at other times of
dress these issues in a multiyear study of the theyear. Duringeachcensus,asearchofthefield
dynamics ofa population ofGeolycosa turricola wasconductedandpreviouslyundiscoveredbur-
(Treat). rows ofspiderlings were marked. We assumed
METHODS in this study that changes in burrow diameter
representedgrowth by the spideroccupyingthat
WestudiedapopulationofGeolycosaturricola burrow. Therefore, the largestdiameter(mm) of
near Starkville, Mississippi, continuously be- each newly discovered and previously marked
tween 1982 and 1985. Thepopulationinhabited burrowwasrecorded. Burrowdiameterhasbeen
shown to be a good indicatorofboth spiderage
'Present address: Department ofScience and Mathe- (McQueen 1978) and size (McQueen 1978; Mil-
matics, Northwest Mississippi Community College ler & Miller 1984) for Geolycosa spiders.
Senatobia, Mississippi 38668 USA The state ofeach burrow was recorded as: (1
50 THEJOURNALOFARACHNOLOGY
active (burrow and burrow turret in good repair the following treatments was assigned to each
and/orspider seen in burrow), (2) open/inactive pie-shapedarea: (1)control(nochange),(2)litter
(burrowandturretindisrepairbutburrowopen- enhanced (addition ofsufficient litter to make a
ing present), (3) disappeared (not found; previ- uniform,2-cmcoverinthearea,(3)denuded(all
ouslymarkedburrowsonly).Burrowingwolfspi- grassandlitterremoved,(4)litterremoved(litter
ders may block the entrance of their burrows raked out, grass left). Because ofthe small num-
with silk and debris during certain times ofthe berofburrowsusedforthisexperiment,wewere
year, particularly during late summer through not able to completely randomize the experi-
spring (Miller & Miller unpublished data). Be- ment. We examined these experimental plots
cause ofthis, every burrow that was scored as duringthenormalcensusandrecordedthenum-
disappeared was reexamined in subsequentcen- ber and size ofthe burrows constructed in each
suses. Renewed activity at a burrow previously plot subsection.
marked as disappeared resulted in the reassign- Statistical comparisons ofaverage burrow di-
ment ofthat burrow as active. ameters between months were made with de-
Weassumedthatburrowsthatappearedactive pendent (paired) i-tests (tj using burrows that
were, in fact, occupied by a spider even though were active in both ofthe months being com-
this was not confirmed in every case. Errors in pared. Independent i-tests {t) were used to com-
thisregardwillleadtoanoverestimationofpop- pare distinct sets ofburrows (e.g., newly discov-
ulation size. However, our intent was to study ered burrows vs previously known burrows).
dispersal timing and survivorship not to make
RESULTS
estimates of population size or density per se.
Wealsoassumedthatburrowswereoccupiedby Comparisons of the reproductive timing of
the original inhabitant. Studies of the activity nearby populations with that ofthe study pop-
patterns of Geolycosa (e.g., McQueen & Culik ulation revealed that the study population had
1981) suggest that this is a reasonable assump- an unusual breeding schedule characterized by
tion. alternating years ofproduction ofyoung. Thus,
Apreliminaryexaminationofthecensusdata althoughsomefemalesmaturedeachyearinoth-
suggested that dispersal involved two groups of er populations, mature females were found only
spiderlings of different size (an early summer inalternatingyears(oddyearsbeginningin 1983)
group ofsmall size and a late summer group of in the study population.
a larger size.) To substantiate this, the size of The tabulation ofthe census data for the gen-
these two groups was compared. The survivor- eration of spiderlings hatched in the spring of
shipofthesetwogroupswascompared overtwo 1983 is given in Table 1. The number ofnewly
winters (1983 and 1984). discovered and previously marked active bur-
Caging experiments were used to determine rowsisgiven foreach month. Thetotal monthly
whetherthebeginningofdispersalcorresponded change in the number ofburrows represents the
to the beginning ofburrow building activity in number of active burrows from the previous
G. turricola. In these studies, a wire cage with a month plus the numberofnewlydiscovered ac-
10 cm radius (fine mesh window screen) was tiveburrows, minusthenumberofburrowsthat
placed over six burrows that contained predis- disappearedsincethe previousmonth(Table 1).
persal young. The inside walls ofthe cages were Burrow construction by spiderlings began in
examined several times each week and spider- Julyand new burrows were discoveredthrough-
lings that were found on the cage wall or on the outthesummer(Table 1). In 1983 atotalof343
ground outside the burrow were scored as dis- burrowsweremarkedbetweenJulyandOctober.
persers and removed. Small crickets were intro- Most(81.0%)werediscoveredinJulyandAugust
duced into the burrow periodically (about once (Table 1). In that year, an average of92.4% of
each week) for food. the burrows marked in one month were active
To determine whether newly dispersed spi- in thenext month (92.7%JulytoAugust, 84.6%
derlings showed any initial burrow site prefer- August to September, 100% September to Oc-
ence we conducted a habitat manipulation ex- tober).
periment in 1985. Prior to dispersal we altered There was an increase in the average burrow
thehabitatwithin 3 mofeightburrowsthatcon- diameter between July and August 1983. The
tainedyoung.Eachcircularareawasdividedinto average diameter ofthe 141 burrows that were
four pie-shaped areas ofequal size, and one of establishedinJulyandrecordedasactiveinAu-
MILLER & mLLEK-GEOLYCOSA POPULATION DYNAMICS 51
Table 1.—Survival historyofacohortofGeolycosa Table2.—Percentageofoverwintersurvivorsofand
turricola.Entriesarethenumberofactiveburrows(see burrow diameters oftwo groups of G. turricola spi-
text). Table includes only spiderlings that hatched in derlings. July 1983 group includesspiderlingsthates-
spring 1983. tablishedburrowsduringJuly 1983,August 1983group
includes spiderlings that established burrows between
Active burrows August and October 1983 (see text).
Pr. Diameter Initial % over-
Date New marked Total (SD) Group burrow size winter
7-83 152 0 152 4.2(1.03)
Firstwinter, 1983
8-83 126 141 267 7.0(1.78)
9-83 60 226 286 6.9(1.62) July 1983 group
10-83 5 286 291 — (TV= 44) 4.2(1.03) 31.6
August 1983 group
Winter (TV= 95) 7.1 (1.78) 68.4
3-84 0 139 139 8.2 (2.21)
Second winter, 1984
4-84 136 139 275 8.3(1.97)
5-84 2 207 209 9.8 (1.61) July 1983 group
6-84 0 149 149 12.3(2.09) (TV= 5) 4.1 (0.98) 23.8
August 1983 group
7-84 0 139 139 14.7(2.61)
8-84 _ — — — (TV= 16) 7.4(1.64) 76.2
9-84 0 5 5 20.0(3.74)
10-84 0 5 5 19.3 (3.04)
Winter forSeptemberofthe previousyear(l^ = 5.51,
3-85 0 50 50 — = 139, F < 0.01; we obtained no burrow di-
—
4-85 0 5 5 ameter estimates for October of 1983). All of
these overwintersurvivors remained active into
April at which time 136 new burrows were dis-
gustincreased from X= 4.2 mm (SD = 1.03) to covered. The average burrow diameter ofthese
X = 6.9 mm (SD = 1.79) {t^ = 11.5, #= 140, new burrows (X= 7.9 mm, SD = 2.93) was not
P < 0.001).Theaveragediameteroftheburrows significantly different than that ofthe 139 over-
that were established in August (X = 7.1 mm, winter survivors {X = 8.7 mm, t = 0.80, df=
SD = 2.11) was significantly larger than the av- 273, P > 0.05). The percentage of spiderlings
erage diameter ofthe July burrows {t = 14.53, that survivedthrough the springand summerof
df= 265, P < 0.001). Therewasnotadifference 1984 was high {X = 85.1%; 100.0% March to
in the diameter of the burrows established in April, 75.3% April to May, 71.9% May to June,
September when compared to the new burrows 93.3% June to July). In the late summer ofthat
ofAugust(/= I33,df= 178,P< 0.001).Because year a large percentage of the burrows disap-
ofthe difference in initial burrow size between peared. A substantial number ofthese burrows
theJulyandAugust spiders, the survivorshipof reappeared as active burrows in the spring of
those two groups was examined separately. 1985 (35.9%; Table 1). During 1984 theaverage
mm
Approximately 48% ofthe burrows that were burrow diameter increased from 8.2 to
mm
establishedinthe summerandfallof1983 (291; around20 (Table 1). Ofthe 50burrowsthat
Table 1) were recorded as active in early 1984 survivedthrough thewinterof 1984-1985, only
(139;Table 1).Ofthese, 31.6%wereofthegroup fiveofthosewererecordedactiveduringAugust
thatinitiallyestablishedtheirburrows inJulyof ofthat year. One ofthose burrows is known to
1983 and 68.4% were ofthe group ofburrows have contained an adult spider with young dur-
discovered in August of 1983 (Table 2). Fifteen ing the spring of 1985.
percentofthoseburrowsthatwereactivein 1984 Theaveragenumberofspiderlingstakenfrom
were still active in 1985. Approximately two- cage walls (TV = 6 cages) during each month of
thirds (76.2%) of these were from the original the 1983 caging experiment were: X = 7.5, SD
August 1983 group (Table 2). = 16.3, July; X = 7.6, SD = 23.4, August; X =
Forty-seven percent ofthe burrows that were 3.0, SD =12.0, September; X = 0.8, SD = 0.9,
activeinOctober 1983reopenedinMarch 1984. October. Thus, 80% ofthe spiderlings found on
The average diameter ofthese spring 1984 bur- cagewallswere found thereduringJuly and Au-
rows was significantly greater than the average gust.Unaltered(control)plotscontainedahigher
52 THEJOURNALOFARACHNOLOGY
percentage of new burrows than any of the 3 retreatsandbuildtheirfirstburrowsinthespring.
treatment plots (control 40.5%, open 16.2%, lit- However, our observations of several hundred
terremoved 10.8%, litteradded 32.4%.) Burrow marked burrows ofthat species in Utah showed
disappearance was higher in the treatment areas thatnewburrowsareconstructedintheearlyfall
(control 12.0%, open 26.3%, litter removed (Miller & Miller unpublished data). The results
14.0%, litter added 18.0%). presented here for G. turricola suggest that both
situationsmayexistinasinglepopulationofthis
DISCUSSION
species. The onset of burrow construction co-
Although G. turricola was originally thought incides with the time at which the most spider-
to have a one-yearlife cycle (Wallace 1942), our lings were found on the walls ofcages providing
observations (Miller & Miller 1987) indicated evidence that some spiderlings construct bur-
thatthespecieshasatwo-yearcyclewithasingle rows immediatelyfollowingdispersal fromtheir
reproductiveperiodduringthesecondyear.This mother’sburrow.However,thecensusdatashow
is similar to that reported for other Geolycosa that this pattern may not hold for all dispersing
(e.g., G. fatifera(Hentz), G. missouriensisChdLm- spiderlings.Alargenumber(136)ofnewburrows
berlin, and G.pikei(Marx); Wallace 1942). Ma- appeared in the early spring of 1984. It is likely
ture males appear only in late August and Sep- that these are spiderlings that hatched in 1983,
temberpriortothefinalmoltofthefemale.These overwintered either in their mother’s burrow or
males may cohabitat with the immature female in a retreat, and then constructed their firstbur-
for a short time prior to her last molt (Miller & rowinthe spring(thestrategysuggestedbyCon-
Miller 1986) at which time courtship and cop- ley 1985). This is supported by the observation
ulation occur. Once mated, females cover the that no young were hatched in the study popu-
entrance to their burrow, overwinter there and lation in spring 1984, and the average diameter
produce egg cases in the spring (Miller & Miller ofthe spring 1984 burrows was nearly the same
1986). Males die after mating in the fall. The as that ofpreviously marked burrows that sur-
young reach reproductive age during the fall of vived the winter of 1983 (Table 1). Moreover,
their second year. In our study population, the theSelmaChalksoilinhabitedbythispopulation
spiders that survived the winter of 1983-1984 is usually dry and replete with small cracks dur-
were, thus, ofthe same cohort ratherthan prog- ing the dispersal period. These soil cracks could
eny ofearlyand latebreedingadultsofthe same provide temporary retreats for dispersing spi-
year. As we discuss below, the differences in the derlings (Miller 1984a).
diameterofinitialburrowsandthetimingofthe Anumberofresearchershaveshownthatbur-
establishment ofthese burrows are probably the row density is not an important factor influenc-
result ofvariation in behaviorrelated to the de- ing the survival of Geolycosa spiders (e.g.,
parturefrom the maternalburrowortheprocess McQueen 1983;Conley 1985).However,theim-
ofburrow establishment itself. portance ofthe position ofthe burrow with re-
Althoughtheimportanceoftheburrowduring specttophysicalfeaturesofthehabitatand,thus,
all ofthe life stages of Geolycosa is widely ac- possiblytocritical resources, may be important.
cepted, there is still considerable uncertainty McQueen (1983) observed that the burrows of
aboutthetimingofinitialburrowestablishment, G.domifexwereusuallyplacedinunshadedopen
the factors that affect the positioningofthe bur- areas. One of us (Miller 1984a) addressed the
rowand the extent to which spiderschange bur- issue ofhabitat preference in a series oflabora-
rowlocationsduringtheirlifetime. With respect tory studies with G. micanopy Wallace and G.
totheestablishmentofthefirstburrow,theques- turricola. In those studies it was shown that the
tionremainsastowhetherspiderlingsbuildbur- tendencytoestablishaburrowwasrelatedtothe
rowsimmediatelyfollowingdispersalorwhether presenceofvegetationandthefeedingexperience
there is a delay between dispersal and burrow of the spiderling. The study also showed that
establishmentduringwhich time spiderlings use thesefactorsdifferedbetweenspecies.Theresults
natural retreats. McQueen (1978) intimates that ofthepresentstudy,thoughlimited,corroborate
constructionoffirstburrowsin G. domifexHan- Miller’s (1984a) study by indicating that in G.
cockcoincidedwithdispersalalthoughlittledata turricola burrow sites in grassy areas and grassy
for this conclusion is given. Conley (1985) has areas with considerable litter are favored over
suggested that spiderlings ofthe western species open, uncovered positions. The mortality ofthe
G. rafaelana(Chamberlin)overwinterin natural spiderlingsthatestablishedburrowsinvegetated
MILLER & MIUJEK-GEOLYCOSA POPULATION DYNAMICS 53
areas was somewhat reduced although the study The reason for the high spiderling survival in
is too limited for a strong conclusion in that re- thispopulationoverthefirstwinterisuncertain.
gard. The factors influencing mortality of dispersing
There is considerable uncertainty about Geolycosaspiderlingsareunknownbutarelikely
whether Geolycosa spiders change burrow loca- to include predation, failure to find a suitable
tionsduringtheirlifetime. Itisgenerallythought burrow site, or parasitism. Mortality factors re-
that such changes are uncommon (e.g., Wallace lated to the density ofburrows are probably not
1942; Conley 1985). Our observations of over important (McQueen 1983; Conley 1985). A
500markedburrowsinMississippi(G. turricola; possible explanation is related to their dispersal
thisstudy)andsouthernUtah{G. mfaelana)tend strategy. A portion ofthe broods ofG. turricola
tosupportthis(Miller&Millerunpublisheddata). remain in the maternal burrow well beyond the
The month-to-monthdecreasein the numberof timewhensuccessfuldispersalispossiblewhere-
previously active burrows is much smaller than as other brood members disperse shortly after
the number ofnewly discoveredburrows. Thus, hatching (Miller 1989). Humphreys (1983) re-
itisunlikelythatthoseburrowsmarkedasnewly portedtheexistenceofaphasicdispersalpattern
discoveredare actually spidersthat have moved in the European tarantulaLycosa tarantula (L.).
burrowlocation.Nevertheless,itispossible(per- Hesuggestedthatsuchamixeddispersalstrategy
haps likely) that some threshold ofsite tenacity mightbeanadvantageintemporallyvaryingen-
existsformosthabitats. Indeed, McQueen(1978) vironments.Miller(1989)hypothesizedthatspi-
suggested that many individuals of the species derlings in these subsocial groups have a higher
G. domifex change burrow locations during the chance ofsurvivingthe first winterbecause they
early spring. The results ofthe present study do build deeper burrows than spiderlings that dis-
notconclusivelyruleoutburrowpositionchanges perse shortly after emergence from the egg case.
in this species, but they do suggest that such ac- Therelationshipbetweenburrowdepthandsur-
tivity is uncommon in the population that we vival was first recognized by Humphreys (1973,
studied. 1978). Although the results presented here do
The early survival ofburrowing wolf spiders not establish a direct link between subsociality
isthoughttobeextremelylow(Humphreys 1976; andthetimingofburrowconstruction,theylend
McQueen 1978, 1983). Humphreys (1976) ob- support to that hypothesis. Spiderlings con-
servedthatoverthree-quartersofthespiderlings structingburrowsinAugustmadelargerburrows
of G. godeffroyi (L. Koch) in the two smallest and enjoyed a higher overwinter survival rate
size classes died. McQueen found thatnearly all than those constructing burrows in July.
(90%) ofthe young ofthe year ofa population It should be noted that ifthe spiderlings dis-
of G. domifex in Canada died within several coveredinAugustare participantsin a subsocial
months of hatching. Estimates of adult survi- group,thetimingoftheirdispersalisearlierthan
vorship suggest that fewer than 10% survive to that predicted from Miller’s (1989) laboratory
reproductive age (usually two to three years) studies. This suggests that the extent to which
(McQueen 1983). Theresultspresentedherecor- extendedtoleranceamongGeolycosabroodmates
roborate the observation oflow survival to re- exists may be mediated by environmental con-
productive age but suggest that high spiderling ditions. Clearly, studies ofthe spatial, temporal
mortalitymaynotbe theruleamongthe species and taxonomic variation in subsocial organiza-
in this genus. tioninthisgenusareneededtodelimitthenature
Firstwintersurvivorshipinourpopulationwas andstrengthoftheseenvironmentalconstraints.
considerably higher than that ofpopulations of Intermsofthetotalnumberofactiveburrows
otherspeciesofGeolycosa(e.g.,McQueen 1983). observedduringthestudy,thesurvivorshipover
Nearly all of the first-year burrows marked as thesecondwinterappearslow.Ofthe 1983group
active in 1983 remained active the following only 50 survived the winter of 1984-1985 and
spring. Further, the survivorship through the were recorded active in the spring of 1985, and
summerof1984appearstobehigh.Thedecrease only five ofthose (1.7% of 1983 active burrows)
in the number of active burrows in the fall of wereobservedtobeactivebeyondMarchofthat
that year is primarily the result of(1) the mor- year. However,whenviewedintermsofthespe-
tality ofadult males that have left theirburrows cies’lifecycle, secondwintersurvivorshipishigh.
tomate(andsubsequentlytodie;seebelow),and Ifit is assumed that there is no sex-related mor-
(2) burrow covering by mated females. talitythenapproximatelyone-halfofthe 139spi-
:
54 THEJOURNALOFARACHNOLOGY
dersthatwereactiveinJulyof1984 weremales. McQueen, D. J. 1978. Field studies ofgrowth, re-
As discussed above, these males would mature, production, and mortality in the burrowing wolf
mate and die prior to the winter of 1984-1985. spiderGeolycosadomifex(Hancock). Can. J. Zook,
The remaining spiders that survive would be- 56:2037-2049.
come mature females and remain in their bur- McQueen, D. J. 1983. Mortality patterns fora pop-
ulation ofburrowingwolfspiders, Geolycosa dom-
rowsduringthewinterof1984-1985 to produce
young the following spring. Thus, the fifty sur- Zifoeoxk(,Ha6n1c:o2c7k5)8,-2l7i6vi7n.gin southern Ontario. Can. J.
vivors of the winter of 1984-1985 represent a McQueen, D. J. &B. M. Culik. 1981. Fieldandlab-
majority of the spiders that would have had a oratoryactivity patternsin theburrowingwolfspi-
chance to survive that winter. derGeolycosadomifex(Hancock).Can.J.Zook,59:
1263-1271.
ACKNOWLEDGMENTS
Miller, G. L. 1984a. The influence ofmicrohabitat
We appreciate the comments of B. Main, J. and prey availability on burrow establishment of
oWfeatvheisr,paTp.eFro.rrWeestatnhdanGk.GS.traBtatkoenr,onMe.arlLyaSdarlalfet,s WyaolulnagceGe(oAlryacnoesaae:tuLryrciocsoildaa(eT)r:eaAt)laanbdorGa.tomriycsatnuodpyy.
Psyche, 91:123-132.
C. Ware, J. Jenkins, and T. Furst for their help Miller, G. L. 1984b. Ballooning in Geolycosa turri-
in the field during portions ofthis study. cola(Treat)andGeolycosapatellonigraWallace:high
LITERATURECITED dispersalfrequenciesinstablehabitats.Can.J.Zook,
62:2110-2111.
Conley, M. R. 1985. Predation versus resource lim- Miller, G. L. 1989. Subsocial organization and be-
itation in survival ofadult burrowing wolfspiders haviorinbroodsoftheobligateburrowingwolfspi-
(Araneae:Lycosidae).Oecologia(Berlin),67:71-75. der Geolycosa turricola (Treat). Can. J. Zook, 67:
Harper, L. 1857. Preliminary report on the geology 819-824.
andagricultureofthestateofMississippi. E.Barks- Miller, G. L. & P. R. Miller. 1984. Correlations of
dale Publishers, Jackson, MS. burrow characteristics and body size in burrowing
Humphreys, W. F. 1973. The environment, biology wolf spiders (Araneae: Lycosidae). Fla. Entomok,
and energetics ofthe wolfspider Lycosa godeffroyi 67:314-317.
(L. Koch 1865). Ph.D. thesis, Australian National Miller, G. L. & P. R. Miller. 1986. Pre-courtship
University, Canberra. cohabitation of mature male and penultimate fe-
Humphreys, W. F. 1976. The population dynamics male Geolycosa turricola (Araneae, Lycosidae). J.
ofan Australian wolfspider, Geolycosa godeffroyi Arachnol., 14:133-134.
(L.Koch 1865)(Araneae:Lycosidae).J.Anim.Ecol., Miller, G. L. & P. R. Miller. 1987. Life cycle and
45:59-80. courtship behavior of the burrowing wolf spider
Humphreys, W. F. 1978. Thermal biology of Geo- Geolycosa turricola (Treat)(Araneae, Lycosidae). J.
lycosa godeffroyi and other burrow inhabiting Ly- Arachnol., 15:385-394.
cosidae(Araneae)inAustralia.Oecologia(Berk),31 Wallace, H. K. 1942. A revision ofthe burrowing
319-347. spidersofthegenusGeolycosa(Araneae,Lycosidae).
Humphreys, W. F. 1983. Temporally diphasic dis- Amer. Midland Natur., 27:1-61.
persalinsiblingsofawolfspider:agameofRussian
roulette? Bull. Br. Arachnol. Soc., 5:124-126. ManuscriptreceivedMay1990,revisedSeptember1990.