A New Species of Wolf Spider, Schizocosa Stridulans (Araneae, Lycosidae)

11 Pages·1991·5.1 MB·English

by  Gail E Stratton

1991. TheJournal ofArachnology 19:29-39
A NEW SPECIES OF WOLF SPIDER,
SCHIZOCOSA STRIDULANS (ARANEAE, LYCOSIDAE)
Gail E. Stratton: Department ofBiology, Albion College, Albion, MI 49224 USA
Abstract. Schizocosa stridulans new species is a sibling species to S. ocreata and S.
rovneri. Both males and females ofS. stridulans are very similar to males and females of
S.ocreataandS.rovneriincolorationandgenitalia,butaresignificantlysmallerincarapace
lengthandwidth. MaturemalesofS.stridulanslackadistinctivetuftofbristlesonthetibia
ofthefirstpairoflegs(presentin maturemalesofS. ocreata, absentin maturemalesof5'.
rovneri)-, however, thetibia, patellaand thedistal 1/3 to 1/2 ofthefemuroflegs I ofmales
ofS.stridulansaredarklypigmented.S.stridulansisfoundinmesicuplandsleaflitterfrom
Tennessee, Kentucky, Illinois, Ohio, Missouri, Mississippi, and Alabama, and sometimes
co-occurswith S. ocreata. Male palps and female epigynaare figured forS. stridulansand
forS. rovneriforthe first time.
The genus Schizocosa Chamberlin consists of lack the bristles on the first pair oflegs, but do
medium sized to large wolfspiders that are rel- have conspicuous pigment on the distal 1/3 of
ativelystrongleggedandkeensighted. Members the femur and on the tibia. While at first it was
ofthis genus are characterized by conspicuous thoughtthey maybe hybridsbetween S. ocreata
andcontrastinglightand darkbands on the car- and S. rovneri (Dondale, pers. comm.), a com-
apaceandabdomen, adistinctembolusandter- parison of the morphology and behavior of
minal apophysisin the palp ofthe male (Fig. 1), ocreata- rovneri hybrids (Stratton & Uetz 1983,
andanexcavatedtransversepieceinthemedian 1986), with these clearly demonstrate that these
septum in the epigynum ofthe female (Fig. 5) forms are not hybrids but are a distinct species.
(Dondale & Redner 1978). Schizocosa ocreata
METHODS
(Hentz) is a member of this genus common
throughout woodlands of the eastern United The anatomical description of5. stridulans is
States. It is frequently called the brush-legged basedonmaturemalesandmaturefemales. Spi-
spiderbecauseofconspicuoustuftsofblackbris- ders collected as immatures were reared to ma-
tlesandblackpigmentationpresenton thetibia, turityinthelaboratory.Anatomicalterminology
patella and basitarsus ofthe first pair oflegs in follows that ofDondale and Redner (1978).
mature males (Fig. 11). In their revision ofthe Scanning electron micrographs were done on
genus, Dondale and Redner (1978) noted that aJEOLJSMT200scanningelectronmicroscope
there were occasional populations in which the at 10 kv. Sampleswere prepared by cleaningul-
tufts ofbristles were reduced or absent. A form trasonicallyfor 3 min andthen runningsamples
lacking tufts and black pigment on the first legs throughadehydratingseriesofalcoholdilutions.
ofmature males has a distinct courtship and is They were air dried and mounted with silver
recognized as a distinct species {Schizocosa rov- paint on SEM stubs. Internal aspects offemales
neri Uetz and Dondale 1979). S. ocreata and S. were first cleared for 30 minutes in enzymatic
rovneri do not interbreed unless the female is solution(contactlenscleaner: 10mg/10 misdis-
anesthetized; thus, their dilfering courtship be- tilledwater),dehydratedinalcoholdilutions,then
haviorservesasanisolatingmechanismbetween air dried and mounted.
the two species (Uetz & Denterlein 1979). Fur- In order to investigate patterns of co-occur-
ther studies by Stratton and Uetz (1981, 1983) renceand potential foroverlapwith relatedspe-
demonstratedthatthetwospeciesareinterfertile cies,collectionsofSchizocosaweremadeinmid-
when forced to mate. west and southern USA forests from March to
A new species ofSchizocosa is described and July 1983-1986. Specialemphasiswasplacedon
figured herein that is sibling to both S. ocreata collecting from floodplain forests along major
andS. rovneri. Maturemales ofthisnewspecies rivers, and theircorresponding uplands. Collec-
30 THEJOURNALOFARACHNOLOGY
lions from the Mississippi State Museum and darkening ofthe tibia, patella and basitarsus of
the Museum ofComparative Zoology were also legsI,ascomparedwiththeirotherlegs. Females
examined. In all collections, mixed assemblages ofS.stridulans,S.rovneriandS.ocreataallhave
ofspecies were noted. pairedexcavations in the transverse piece ofthe
Schizocosa stridulans, new species median septum (Figs. 5, 7, 9). In each ofthese,
the distance between the surface excavations is
Figs. 1, 5, 6, 13 lessthanthewidthofoneexcavation. Infemales
Type Material.—Male holotype from Illinois, of S. crassipes, the distance between the exca-
Mason Co., Sand Ridge State Forest, June 1985 vations is greater than on the width ofone ex-
(G. Strattonand L. Hartz), depositedat the Mu- cavation (refer to Dondale «fe Redner’s key to
seum ofComparative Zoology (MCZ), Harvard females,couplet 5, p. 149 (1978)). Spermathecae
University. of S. stridulans, S. rovneri and S. ocreata are
Etymology.—The species name refers to the illustrated in Figs. 6, 8, 10.
primary method ofsound production by males Males.—Totallength,carapacelengthandcar-
during courtship behavior. apace width as reported in Table 1. Carapace
—
Diagnosis. 5. stridulans is significantly brown; pale submarginal band slender, usually
smaller than either S. ocreata (as reported by distinct and undulating, rarely extendingto car-
Dondale & Redner 1978) or S. rovneri (as re- apacemargins;palemedianbandaswideaspos-
ported by Uetz & Dondale 1979; Table 1), al- teriorlateraleyes(mean0.85 mm), withsmooth
thoughthe overlapin sizesofthesethree species marginsandnarrowingslightlyinposteriorthird
makessizeanunreliablecharacter(Table 1). Both ofcarapace. Sternum yellow brown. Chelicerae
malesandfemalesareindistinguishableanatom- brown, setaceous, with three uneven teeth on
ically from those of S. ocreata and S. rovneri promargin offang furrow and three even teeth
exceptforthepatternofpigmentationonthefirst on retromargin. Legs II to IV yellow with dark
pair oflegs ofmature males. Both sexes key to annulations particularly on femurand tibia. Fe-
S. ocreata in the key provided in Dondale and mur ofleg I with black pigmentation on distal
Redner’s (1978) revision ofthe genus. Females half to third; tibia and patella of leg I usually
canbeconfidentlyidentifiedonlywhencollected uniformlyblack(restoflegyellow)(Fig. 13). Pig-
in association with males. In males of S. stri- mentation on femur sometimes streaked. Tibial
dulans, the tibia, patella and distal 1/3 to 1/2 of brush in form ofshort black hairs that increase
mm
thefemurareblack(Fig. 13).Therearefineblack theapparentwidth ofthe tibiabyabout0.2
hairs on the tibia ofmale S. stridulans distinct (widthoftibia: 0.54;widthoftibia -I- hairs:0.75;
from the tibial tufts ofbristles found in the ma- 15 specimensmeasured). DarkareasoflegIwith
ture male S. ocreata (Fig. 11). Mature males of theappearanceofa“five-o-clockshadow”. Dor-
S. rovneri lack both the tufts ofbristles and the sum ofabdomen usuallywith heart mark (14 of
solidpigmentationonthetibiaoflegsI(Fig. 12), 15 specimens), without chevrons. Cymbium of
although these legs may be annulated. Males of palp without terminal macrosetae but with con-
5”. stridulans, S. rovneriand 5. ocreataare iden- centration of bristles. Palea of palp with long
tical with respect to length and angle of paleal distal process, and with a furrow marking off
process ofpalp, median apophysis and with re- rugose prominence on retrolateral side. Median
specttorugoseprominencealongtheretrolateral apophysis with distal margin convex and un-
side ofthe paleal process (Figs. 1-3); this com- dulating. Intromittent part of embolus slender
pareswiththepalpofS.crassipes(Fig.4),amore andpointed.Terminalapophysiswiththickened
southern species that has a smooth prominence margin concealing base of intromittent part of
along the retrolateral side ofthe paleal process. embolus (Fig. 1).
This last charactercorrespondswith couplet #3, Females.—Total length, carapace length and
p. 147 in Dondale and Redner’s (1978) key. carapacewidthasreportedinTableI.Coloration
Mature females of5. stridulans have a slight similar to that of male but with the following
Figures 1-4.—VentralaspectofleftpalpofSchizocosaspecies: 1, S. stridulans-, 1, S. rovneri-, 3, S. ocreata-, 4,
S. crassipes. ipe = intromittentportionofembolus; ma = median apophysis; ppr = paleal process; rp = rugose
prominence; sp = smooth prominence; ta = terminal apophysis. Scale bars = 200 microns.

32 THEJOURNALOFARACHNOLOGY
Table 1.—Comparison oftotal length, carapace length and carapace width ofS. stridulans n.sp., S. ocreata
(data from Dondale & Redner 1978), and 5. rovneri(data from Uetz & Dondale 1979). Measurements are in
mm. Where sample size is greater than 10 individuals, carapace measurements are given as means ± their
standarddeviations. Values followedby the same letterare not significantlydifferentfromeach other(1 tailed
t test, P < 0.05).
S. ocreata S. rovneri S. stridulans
MALES
Total length(ranges) 5.65-8.30 6.48-8.00 5.04-6.80
(mean) 6.40 ± 0.43
Carapace length(means) 3.65 ± 0.43 A 3.73 A 3.25 ± 0.33 B
(ranges) 3.48-4.02 2.47-3.80
Carapace width(means) 2.78 ± 0.34C 2.77 C 2.56 ± 0.24 D
(ranges) 2.57-2.95 2.04-3.10
Sample size 20 7 51
FEMALES
Total length(ranges) 7.30-10.40 6.01-7.95 6.56-11.36
(means) 8.09 ± 1.21
Carapace length(means) 4.00 ± 0.43 E 3.91 E 3.50 ± 0.40 F
(ranges) 3.45-4.28 2.63-^.27
Carapace width(means) 3.02 ± 0.31 G 2.93 G 2.68 ± 0.35 H
(ranges) 2.64-3.24 1.88-3.21
Sample size 20 7 61
exceptions. Pale median band on prosoma 0.96 dulans will rarely court females of either S.
mm
wide behind eyes and usually narrowed in ocreata or S. rovneri. Females ofthe other spe-
posteriorhalfofcarapace. Cheliceraeasin male. cies are not receptive to courting males of S.
LegsItoIVyellowwithdarkannulations. Tibia, stridulans. Females of S. stridulans are not re-
basitarsusandoccasionallypatellaoflegIdarker ceptive to courting males ofother species.
thanonotherlegs,withannulationslessdistinct. Geographicdistributionand habitat.—Collec-
Epigynumwithmoderatelydeepatrium;median tions of S. stridulans have been made from
septumwithlongitudinalpiecebroadposteriorly southern Ohio, Illinois, Kentucky, Tennessee,
and usually narrowing anteriorly with lateral Missouri,AlabamaandMississippi(Fig. 14),thus
edgesconcave. Transversepiecewithlargepaired giving it broad geographic overlap with both S.
excavations,theseexcavationsnearlymeetingat rovneri and S. ocreata. The habitat of S. stri-
midline.In7of15individuals,theseexcavations dulans is mesic uplands leaf litter, typically in
asymmetrical in size and sometimes in shape. oak forests or oak hickory forests (Fig. 16). The
Distance between excavations varying from al- present study also extends the known range of
most no space to a separation slightly less than S. rovneri.
the width ofa single excavation. Spermathecae In two ofeight localities visited in 1984 and
ovoid,smooth,separatedbyapproximatelytheir 1985, S. stridulanswas the only Schizocosa col-
width. lected in the uplands forests (Figs. 15, 16). In
Courtship behavior.—Males of S. stridulans three collections, 5. stridulans occurred in the
clearly differ from S. ocreata and S. rovneri in same habitat as S. ocreata (Figs. 15, 16), and in
sexual behavior. The courtship ofS. stridulans one collection from Alabama it also occurred
consists ofpulses ofstridulation ofthe palp, in- withapopulationthatispossiblyanundescribed
terspersed with tapping ofthe first pair oflegs. specieswithinthisspeciescomplex(Strattonun-
A full description ofthe courtship behavior, the publ. data). Table 2 summarizes 46 collections
sounds produced duringcourtship, the variabil- ofSchizocosaandindicateswhetherspecieswere
ity ofthe various components ofthe behavior, collectedalone,orco-occurredwithotherspecies
and the results ofattempted cross matings is in in the species group which includes 5. ocreata,
preparation (Stratton, in prep.). MalesofS. stri- S. rovneri, S. stridulansandthesouthernspecies
STRATTON-5C///Z<9C05'.4 STRIDULANS, NEW SPECIES 33
Figures 5-10.—Externaland internal aspects ofepigyna ofSchizocosa: 5, external aspect ofS. stridulans; 7,
external aspect S. rovneri\ 9, external aspect S. ocreata; 6, spermatheca ofS. stridulans', 8, spermatheca ofS.
rovneri', 10, spermatheca ofS. ocreata. at = atrium; ex = excavation; ms = median septum; tp = transverse
piece. Scale bars = 100 microns.
34 THEJOURNALOFARACHNOLOGY
Figures 11-13.—Legs I ofmature males ofSchizocosa: 11,5'. ocreata\ 12, S. rovneri\ 13, S. stridulans.
S. crassipesandS floridana. In mostcollections behavioris potentiallyimportantasan isolating
.
each ofthese species was found alone, although mechanism. This has been studied extensively
S. ocreataandS. rovnerisometimesco-occurred for S. ocreata and S. rovneri (Stratton & Uetz
asdid5. ocreataandS. stridulans. Thissuggests 1981, 1983, 1986) but to a more limited extent
that for the species that do co-occur, courtship inS.stridulansandS.ocreata(Stratton,inprep).
More is known ofthe habitat preferences for
Table2.—Co-occurrenceofspecieswithintheSchi- S. ocreatathanfortheotherspeciesinthegenus,
zocosaocreataspeciescomplex. Eachentryrepresents and this preference appears to vary geographi-
a separate collection. Collections were by the author, cally. Dondale and Redner(1978) reportthat S.
by Wayne Maddison and from the Mississippi State ocreata tend to be found in moist areas relative
Museum. to S. crassipes and S. floridana. In North and
South Carolina, Missouri (Big Oak Tree State
S. S. .S. 5. 5. Park), as well as in Sand Ridge State Forest in
oc- rov- stri- eras- flori- central Illinois, S. ocreata was collected on the
reata neri dulans sipes dana floodplains ofrivers or near wet areas. For ex-
S. ocreata 13 ample, along the flood plain ofthe Tyger River
S. rovneri 3 12 inS.Carolina,S.ocreataappearedtobethemost
S. stridulans 3 0 6 abundantwolfspider;inBigOakTreeStatePark,
S. crassipes 1 1 1 4 a virgin floodplain forest along the Mississippi
S.floridana 0 0 0 1 1 River in Missouri, S. ocreata again appeared to
STRATTON-5C///Z(9CO&4 STRIDULANS, NEW SPECIES 35
bethe mostabundantwolfspider(Fig. 17). Col- enceorabsenceofothercompetingspecies.Cady
lections in Illinois, Kentucky, and Ohio yielded (1983) in a study in south central Ohio, reports
S. ocreata from the drier uplands and often on that S. ocreata is closely restricted in its micro-
slopes above major rivers (Fig. 16), while other habitat and that its distribution and locomotor
species (particularly S. rovneri) were found on activityarerelatedto moistureand physical fea-
floodplains and bottomlands (Fig. 17). Perhaps tures of the microhabitat. Cady found that S.
the habitat “preference” ofS. ocreata may par- ocreata was more likely to be found in full leaf
tiallydependongeographiclocality(anditsmany litter rather than in sparse litter, and that the
associated factors) and/or possibly on the pres- species preferred areas ofhigh soil moisture. He
36 THEJOURNALOFARACHNOLOGY
IL Ml IL MA
Figure 15.—Comparison ofrelative numbers of5. stridulans n. sp. and related species in floodplain forest
and uplands forest along major river systems in the U.S. Midwest. The X-axis ofeach graph shows numbers
ofspiderscollected/person-hour(mostcollectionswere 2-3 person-hours). Collectionsweredonebytheauthor
in 1984 and 1985. From top and clockwise: IL MI = Illinois: Marshall Co., State Fish and Wildlife Area; IL
MA = Illinois: Bureau Co., Miller Anderson Nature Preserve; IL AL = Illinois: Alexander Co.; KY CB =
Kentucky: Hickman Co., Columbus-Belmont Battlefield State Park; AL Ld = Alabama: LauderdaleCo. (along
Tennessee River); MO B.O.T. = Missouri: MississippiCo., BigOakTreeStatePark; MOTT = Missouri: Cape
STRATTON-^C/Z/ZOCOS/l STRIDULANS, NEW SPECIES 37
^
Key: oereata
0
rovneri
stridulans
1 I
^
species “B”
sa> Mo TT
a
m
k«.
n
E
Rivers: IL IL Mi/IL IL Mi Mo Mi Tn
Figure 16.—Comparisonofrelative numbersofSchizocosaspeciescollected from uplandshabitat. Key as in
Fig. 15.
suggeststhatmicrohabitatselectionbyS.oereata These populations and their habitats were in-
is important in courtship. vestigated in some detail and will be reported
ThehabitatofS.rovneriisgenerallyfloodplain separately (Stratton, in prep).
forests (Uetz & Dondale 1979; Stratton & Uetz The distribution patterns within this complex
1981, and Fig. 17), although there are reported ofthree sibling species are intriguing. While S.
collectionsof5.rovnerifromseveraluplandhab- oereata and S. rovneri are sympatric and occa-
itats in the Cincinnati area (G. W. Uetz, pers. sionally syntopic, and while S. oereata and S.
comm.)and in Illinois (Fig. 16). The spidersare stridulansare also occasionally syntopic, S. stri-
most frequently found in or on flattened mud dulans and S', rovneri are apparently never syn-
packed leaflitter, orin and on piles ofdrift that topic. Itappearsthatboth S. rovneriand S. stri-
are frequently found in these flood prone eco- dulans are stenotypic, whereas S. oereata is
systems. comparatively eurytypic. More investigations
InCentralIllinois(MasonCounty),S.oereata, withthedetailofCady’s(1983)studyareneeded
S. rovneri and S. stridulans were all found in to understand the interactioh of these spiders
closeproximitytoeachother.S.rovneriwasfound with their habitat.
in the Chautauqua National Wildlife Refuge, Itappearsthatcourtshipbehaviorofthesespe-
along the Illinois River. It was also collected in cies may be very habitat specific. It is hypothe-
other floodplain forests alongthe Illinois River. sized that the stridulatory component of the
ApopulationofS.oereatawasfoundinaswampy courtship behavior in S. stridulans may be in-
areawithin the Sand Ridge State Forest. An ad- audible (and ineffective) on anything but dry
jacent area that was slightly higher in elevation leaves. The courtship behavior ofS. stridulans
and slightly more mesic yielded S. stridulans. is most similar to that of S. crassipes and S.
Girardeau Co., Trail ofTears State Park; MO St C/Bab = Missouri: St. Louis Co., Babler State Park; IL Cl =
Illinois:CalhounCo.,RedsLandingWaterfowlManagementArea;ILPM =Illinois:JerseyCo.,PereMarquette
State Park.
38 THEJOURNALOFARACHNOLOGY
24- Schizocosa species, Floodplains Key: rovneri
22- ocreata
20-
IL Al
18-
16
IL Ml
14
12
10-
MoStC
8- IL Cl
6
MA
IL
4-1
2
Rivers: IL IL IL Mi/IL Mo Mi Mi Ty
Figure 17.—ComparisonofrelativenumbersofSchizocosaspeciescollectedfrom floodplainhabitats. Keyas
in Fig. 15.
floridana (Stratton in prep), both of which are Cross), 7 males(MSM);ClaiborneCo., RockySprings
alsorestrictedtomesichabitats(Dondale&Red- Park, 17 May 1983 (W. P. Maddison), 5 males, 6 fe-
ner 1978; Stratton, unpubl. data). Through this males(MCZ). (Note: MCZreferstoMuseumofCom-
study and others, a more complete understand- parative Zoology, Harvard University, MSM to Mis-
sissippi State Museum, and GES to the personal
ingofSchizocosastridulanswillcontributetoour
collection ofthe author.)
understanding ofthe evolution ofthis genus.
Materialexamined.—USA:lllinios:MasonCo.,Sand ACKNOWLEDGMENTS
Ridge State Forest, May-June 1985 (G. Stratton and
L. Hartz), 15 males, 15 females (MCZ); Jersey Co., ThanksareextendedtoG.Uetzforhisongoing
PereMarquetteStatePark, 29 May 1984(G. Stratton, interest and support and to C. Dondale for ex-
L.Williams),4males(GES). Ohio:AthensCo.,Strouds amining specimens and providing encourage-
Run StatePark,June 1986 (J. Rovner), 1 male(GES). ment. The comments ofA. Brady and C. Don-
Missouri:StLouisCo.,BablerStatePark, 1 June 1984 dale greatly improved the quality of the
(G. Stratton, L. Williams), 10 males (GES); Cape Gi- manuscript. I wish to thank W. Maddison for
rardeauCo.,TrailofTearsStatePark,OakForestUp-
collecting wolfspiders, and to L. Williams and
lands, 25 June 1984 (G. StrattonandL. Williams), 18
Dm.aavleys,Cr1o1ckfeetmtalSetsat(eMPCaZr)k,.rTaevninneesssleoep:e,La1w6rMeancye1C9o8.3, aL.reHeaxrttezndfoerdatsosiRs.taSncchemiwtittehrffioelrdtweoarchki.ngThmaenktso
(W. P. Maddison), 9 males, 7 females (MCZ); Knox use the scanning electron microscope. B. Gib-
Co., near Powell, oak forest, 23, 30 June 1981 (G. bons provided the drawings ofthe legs and M.
Stratton),5males, 12females(MCZ). Kentucky: Row- Knapp helped with some ofthe measurements.
an Co., Daniel Boone National Forest, Twin Knob Financial support was provided by the Cottrell
Recreation Area, 14 May 1983 (W. P. Maddison), 4 ResearchCorporationandBradleyBoardforRe-
males,3females(MCZ);HickmanCo.,ColumbusBel- search and Creativity.
montBattleFieldStatePark,3June 1984(G.Stratton,
L.Williams) 1 male(GES).Alabama: LauderdaleCo., LITERATURECITED
aboveTennesseeRiver, 18 June 1984(G. Stratton, L.
Williams), 1 male, 1 female (GES). Mississippi: Pon- Cady, A. B. 1984. Microhabitat selection and loco-
totoc Co., Natchez Trace Parkway, 17 May 1983 (W. motor activity ofSchizocosa ocreata (Walckenaer)
P. Maddison), 4 females (MCZ), 1 mi. SE of Ecru, (Araneae: Lycosidae). J. Arachnol., 11:297-307.
pitfall in deciduous forests May-June 1980 (W. H. Dondale, C. D. & J. H. Redner. 1978. Revision of