prey-capture by jumping spiders - american arachnological society

1998. The Journal of Arachnology 26 :369-381

A CASE OF BLIND SPIDER'S BUFF?: PREY-CAPTURE BYJUMPING SPIDERS (ARANEAE, SALTICIDAE) IN THE

ABSENCE OF VISUAL CUES

P.W. Taylorl' 2 , R.R. Jackson', and M.W. Robertson' 3 : 'Department of Zoology,University of Canterbury, EO . Box 4800, Christchurch 1, New Zealand

ABSTRACT. Jumping spiders (Salticidae) are well known for their complex visual hunting behavior,but this is the first comparative study investigating their ability to catch prey in the absence of visual cues .When tested with vision occluded inside tubes, where spiders and prey (house flies, Musca domestica,and fruit flies, Drosophila spp .) could not easily evade each other, each of 42 salticid species tested caughtprey in at least one of five different procedures used. Some salticids caught flies less frequently or wereless aggressive when tested in petri dishes, where spiders and flies could easily evade each other . For bothtypes of arena and prey, there were significant species differences in both success at prey-capture andtendency to respond aggressively when first contacted by flies . Additionally, there was significant positivecorrelation between success at catching prey and tendency to act aggressively when first contacted . Sal-ticids resembled short-sighted spiders from other families by only attempting to catch flies when physicallycontacted, and by rapidly leaning forward ('lunging') to catch prey rather than leaping as they do whenvisual cues are available. We discuss circumstances in nature when an ability to catch prey in the absenceof visual cues might be used by salticids .

Jumping spiders (Salticidae) have visualacuity that far exceeds the abilities of otherspiders (Land 1985 ; Blest et al . 1990) and arewell known for their use of vision when com-municating (Crane 1949 ; Clark & Uetz 1994),navigating (Hill 1979; Tarsitano & Jackson1997) and hunting (Forster 1977, 1979 ; Jack-son & Pollard 1996 ; Bear & Hasson 1997 ; Liet al. 1997). Although members of some otherspider families do use vision when hunting(e.g ., Snelling 1983 ; Stratton 1984; Jackson etal. 1995), no non-salticid comes close to therefinement of vision-mediated hunting behav-ior used routinely by salticids . After orientingtoward a target, a salticid relies mainly on vi-sual cues when making decisions aboutwhether and how a hunt should proceed (For-ster 1977 ; Jackson & Pollard 1996 ; Li & Jack-son 1996) . For example, visual cues aboutprey identity, size, distance and orientation in-fluence the salticid's speed and direction ofapproach (Dill 1974; Freed 1984 ; Jackson &van Olphen 1991 ; Bear & Hasson 1997). The

2 Current address : Department of Entomology,The Hebrew University of Jerusalem, PO . Box 12,Rehovot 76-100 Israel .I Current address : Biology Department, MillikinUniversity, Decatur, Illinois 62522-2084 USA .

369

salticid slowly creeps up on its prey untilclose enough for an attack, pauses, and thenfinally leaps at the prey (Heil 1936 ; Drees1952; Forster 1977) .

Despite their remarkable adaptation for di-urnal activity, salticids appear able to coordi-nate some activities in darkness. For example,when in darkness, salticids can maintainstraight courses by turn-alternation (Taylor1995) and communicate by vibratory signalstransmitted through nests (Richman & Jack-son 1992) . These non-visual abilities promptspeculation about whether salticids can alsocatch prey when visual cues are not available .Laboratory studies addressing this issue haveyielded conflicting evidence ; when tested inlarge arenas, Phidippus johnsoni (Peckham &Peckham 1883) failed to catch prey in the ab-sence of visual cues (Jackson 1977), but Triteplaniceps Simon 1899 was later found tocatch prey when tested in smaller arenas (For-ster 1982) . Trite planiceps lives in dark re-cesses formed by rolled-up leaves, and adultsusually do not build enclosing retreats (seeTaylor 1997). Forster (1982) suggested thatthis species' ability to catch prey in the ab-sence of visual cues is related to its lifestylepromoting frequent encounters with potentialprey in darkness . Evaluation of whether Trite

370

planiceps is unusual in its ability to catch preyin the absence of visual cues requires com-parative data from a broad array of salticidspecies from this large and diverse spider fam-ily (see Coddington & Levi 1991) .

In this paper we investigated the non-visualprey-catching abilities of salticids from 17subfamilies, including representatives of di-verse lifestyles (e .g., foliage-dwellers, ground-dwellers, active hunters, ambush hunters,web-invading araneophages, web-builders,ant-mimics, myrmecophages) and geographicregions (Table 1) . For comparative purposes,we also investigated the non-visual prey-catching abilities of some non-salticid huntingspiders (i .e ., spiders with comparatively pooreyesight) from the same habitat as Trite plan-iceps .

Because salticid eyes are not sensitive toinfra-red light (Blest et al . 1981 ; Yamashita1985; Peaslee & Wilson 1989), infra-red videowas used to observe the behavior of spidersin the absence of visual cues . This is amongstthe first studies to make use of this technologyto study the behavior of salticids (see alsoTaylor 1995) .

METHODSSpiders from laboratory cultures were used

(Table 1), excluding individuals that weremissing appendages . Standard maintenanceprocedures were used (Jackson & Hallas1986). Except during experiments, spiders hadad libitum access to adult house flies (Muscadomestica) or adult fruit flies (Drosophilamelanogaster) as prey, depending on the spi-der's size . Portia spp., which prefer spiders asprey, had their diets supplemented with vari-ous species of spiders, and Corythalia canosa,Natta rufopicta and Zenodorus orbiculatus,each of which prefers ants, had their diets sup-plemented with various species of ants .Voucher specimens of all spiders used havebeen deposited (by RRJ) at the Florida StateCollection of Arthropods (Gainesville) .

Five different testing procedures were used,but all had the six following elements in com-mon: 1) All tests were carried out during thelaboratory light phase (12L :12D), excludingthe first and last 2 h . 2) Between tests, arenaswere thoroughly washed with water and thenethanol to remove silk and chemical cues thatmay have accumulated during previous tests .3) Prior to testing, spiders were kept without

THE JOURNAL OF ARACHNOLOGY

food for 6-8 days . 4) Spiders were tested onlyonce per day. 5) Individual spiders were testedin the dark using only types of prey that theyhad been observed catching in the light . 6)Spiders were used only once with each preytype in any type of test .

Blinded spiders in horizontal tubes .-Two days after feeding and six days prior totesting, all eyes of the test spider were coatedwith two or three layers of opaque enamelpaint while the spider was subdued underCOZ. A spider and an adult fly (M. domesticaor vestigial-winged D. melanogaster) wereplaced at opposite ends of a 120 mm-longclear plastic tube plugged by a cork at eachend. The spider and fly were separated by apartition placed in a slit at the tube mid-point .Spiders and flies were then left for 5 min tosettle down before tests were started . To starta test, the partition was removed so that spi-ders and flies could move around the entirearena. Spiders were observed for 15 min oruntil predation occurred .

Spiders 6.0 mm or less in body length weretested in 6.4 mm diameter tubes, whereas spi-ders 6-8 mm in body length were tested in7.9 mm diameter tubes . Adult females wereused for tests of species in which adult bodylength was 8 mm or less . Juveniles 6-8 mmin body length were used for species in whichadult body length was greater than 8 mm .

Blinded spiders in vertical tubes.-Thesetests were used primarily for species thatfailed to catch flies when blinded and in hor-izontal tubes. Tests using blinded spiders inhorizontal tubes and in vertical tubes wereidentical except for tube orientation . Spiderswere placed in the uppermost half of the tube .Because flies tend to move upwards when giv-en the opportunity, this procedure was adopt-ed as a means of promoting more frequentcontact between spiders and flies than in testsusing horizontal tubes .

Sighted spiders in tubes .-Tests withsighted spiders in tubes were the same as testsusing blinded spiders in horizontal tubes ex-cept that the arena was made of glass ratherthan plastic and, instead of blinding the spi-ders, they were observed using infra-red (IR)video. Tests were staged inside a light-proofcabinet (800 mm high, 1200 mm long, 500mm deep) illuminated by an infra-red lightsource (GTE Mini Kat narrow angle IR illu-minator) and were observed using a video-

TAYLOR ET AL.-SALTICID NON-VISUAL PREY CAPTURE

371

camera that was sensitive to IR light (BurleTC300E CCD). The IR video camera wasconnected to a monitor positioned outside thecabinet so that behavior of spiders could beobserved. Because the video field of view en-compassed the whole arena there was no needto track the spiders and flies as they movedabout during experiments . The light-proofcabinet had sleeves (500 mm long), consistingof a double layer of heavy black satin, at-tached to a 150 mm diameter hole in the wallso that the experimenter could reach in to re-move the partition (i .e ., begin tests) withoutallowing light to enter .

Rather than varying the tube diameter withspider size, only adult spiders were used andall spiders were tested in tubes that were 100mm in length and 11 mm in internal diameter.Fruit flies used were fully winged Drosophilaimmigrans instead of vestigial winged D. mel-anogaster . Drosophila immigrans is largerand more active in darkness than is D. mela-nogaster, and the spiders and flies contactedeach other more frequently when this specieswas used in preliminary tests . Instead of ad-justing prey size to spider size, all spiderswere tested using a `standard fruit fly' 2 .5-3mm in body length or a `standard house fly'7-8 mm in body length. After placing a flyand a spider at opposite ends of the tube withthe partition in place, the tube was placed hor-izontally in the light proof cabinet . The par-tition was removed in IR light after the spidershad been in IR light for a 5 min settling-downperiod. Each test lasted 15 min or until thespider caught the fly .

In preliminary tests, individual spiders re-sponded to contact with the flies in one ofseveral different ways . A spider might re-spond in an apparently aggressive manner; itmight actually lunge at the fly (rapidly leanforward by extending Legs III and IV, tarsi ofthese legs remaining on the substrate) and at-tempt to grasp it with the front legs, or itmight carry out apparent preliminaries tolunges, such as orienting toward the fly orraising its front legs . These responses werecollectively termed `confront' . Alternatively, aspider might respond in an apparently less ag-gressive manner; it might run, walk, or leap(all tarsi leave the substrate) away from thefly, turn away from the fly without stepping,or lean away from the fly by flexing legs onthe side opposite to the fly. These responses

were collectively termed `avoid' . Whetherspiders and flies physically contacted eachother during the 15 min testing period wasrecorded and responses of spiders to first con-tact with the fly were recorded as either con-front or avoid . The tendency to confront, rath-er than avoid, flies provided a general measureof `aggressiveness' .

If flies were grasped and then released, orif they broke free from spiders during tests,these spiders and flies were kept in IR lightfor a further 60 min after the 15 min testingperiod ended. This enabled us to investigatewhether the flies died and, if the flies died,whether the spiders later picked up the deadflies and ate them. When flies died after beingbitten, this was recorded as a capture .

Sighted spiders in petri dishes .-The are-na used here was a plastic petri dish (85 mmdiameter) with a plastic tube (30 mm long, 7mm internal diameter) glued onto a hole in thewall. A standard house fly (i .e ., 7-8 mm bodylength) was placed into the tube . A partitioninserted into a slit at the petri dish end of thetube and a wooden plunger inserted into theother end of the tube prevented the fly's es-cape. Next, the test spider was placed in thepetri dish and the arena was placed into thelight-proof cabinet . After a 5 min settling-down period, the partition was removed . Theentry of the fly into the dish defined the be-ginning of the test. As soon as the test began,the plunger was depressed so that neither thespider nor the fly could leave the petri dish .Tests lasted 15 min or until prey capture, andwere observed using IR video (see above) .These tests are the closest approximation inthe present study to the procedures used byJackson (1977) and Forster (1982) to investi-gate non-visual predation in the salticids Phi-dippus johnsoni and Trite planiceps, respec-tively, but with the improvement of being ableto observe the behavior of the spiders .

Sighted spiders in darkness vs . light.-Inthese tests, we assessed differences in the fre-quency with which individual spiders caughtflies in darkness versus light. The general pro-cedure resembled tests using blinded spidersin horizontal tubes except that spiders werenot blinded. Instead, each individual spiderwas tested once in the light and once in dark-ness on successive days (in random order) . Tobegin tests in darkness, the tubes were placedhorizontally in a light-proof cabinet as soon

Tabl

e 1.-Spider

s te

sted

for

abi

lity

to

catc

h pr

ey i

n th

e ab

senc

e of

vis

ual

cues

.

Subfamily

(Family')

Origin

Typical adult

body length

(mm)

Salt

icid

sAsemonea tenuipes O. PCa

mbri

dge

1869

Lyss

oman

inae

Sri

Lank

a4

Bavi

a ae

rice

psSimo

n 18

77Th

iodi

nina

eAu

stra

lia

(Que

ensl

and)

12Co

ryth

alia

can

osa(W

alck

enae

r 18

37)

Plexippinae

USA (Florida)

6Co

smop

hasi

s bi

taen

iata

(Keyserling 1882)

Heliophaninae

Aust

rali

a (Q

ueen

slan

d)6

Cosm

opha

sis

mica

rioi

des

(L.

Koch

188

0)Heliophaninae

Aust

rali

a (Q

ueen

slan

d)7

Cosmophasis sp

.Heliophaninae

Philippines

7Cy

rba

ocel

lata

(Kroneberg 1875)

Spar

taei

nae

Sri

Lank

a5

Epeu

s sp

. 1

Hyllinae

Singapore

8Epeussp

. 2

Hyllinae

Philippines

8Er

is m

argi

nata

(Wal

cken

aer

1837

)De

ndry

phan

tina

eUSA

6Eu

ophrys parvula

Brya

nt 1

905

Euophrynae

New

Zeal

and

6Euryattus sp

.Cy

taei

nae

Aust

rali

a (Q

ueen

slan

d)8

Hasari

us a

dans

oni

(Andouin 1827)

Hasariinae

Aust

rali

a (Q

ueen

slan

d)6

Help

is m

init

abun

da(L

. Ko

ch 1

880)

Astianae

New

Zeal

and

7Hentzia mitrata

(Hen

tz 1

846)

Dend

ryph

anti

nae

USA

(Nor

th C

arol

ina)

5Ho

lopl

atys

pla

niss

ima(L

.Koc

h 18

79)

Marp

issi

nae

New

Zeal

and

8Ho

lopl

atys

sp.

Marpissinae

New

Zeal

and

5Ja

ckso

noid

es q

ueen

slan

dicu

sWanless 1988

Asti

anae

Aust

rali

a (Q

ueen

slan

d)7

Lyss

oman

es v

irid

is(W

alck

enae

r 18

37)

Lyss

oman

inae

USA (Florida)

6Ma

rpis

sa m

arin

aGo

yen

1892

Marp

issi

nae

New

Zeal

and

8Meneme

rus

biva

ttat

us(D

ufou

r 18

31)

Marp

issi

nae

Aust

rali

a (Q

ueen

slan

d)5

Mogr

us d

umic

ola

(0. PCa

mbri

dge

1872

)De

ndry

phan

tina

eIs

rael

8Mopsus mormonKa

rsch

187

8Thyeninae

Aust

rali

a (Q

ueen

slan

d)12

Myrm

arac

hne

lupa

taL

.Koch 1879

Myrmarachninae

Aust

rali

a (Q

ueen

slan

d)5

Natt

a ru

fopi

ctaSimo

n 19

01Heliophaninae

Kenya

5Ph

idip

pus

john

soni

(Peckham & Peckham 1883)

Dend

ryph

anti

nae

USA

(Cal

ifor

nia)

9Ph

idip

pus

sp. 1

Dendryphantinae

USA

(Ari

zona

)9

Phidippussp

. 2

Dend

ryph

anti

nae

USA

(Tex

as)

9Plexippus calcaratus

Kars

ch 1

880

Plexippinae

Aust

rali

a (Q

ueen

slan

d)10

Portia africana(Sim

on 1

886)

Spar

taei

nae

Kenya

8Port

ia j

imbr

iata

(Doleschall 1859)

Spar

taei

nae

Aust

rali

a (Q

ueen

slan

d)8

Port

ia l

abia

ta(T

hore

ll 1

882)

Spar

taei

nae

Sri Lanka, Philippines

8

H C r 0 z m H a r I aTable 1.-Continued.

r H nTy

pica

l ad

ult

dSubfamily

body length

z(Family')

Origin

(mm)

O zPortia schultziKars

ch 1

878

Spar

taei

nae

Kenya

7

cSi

maet

ha p

aetu

la(K

eyse

rlin

g 18

82)

Sima

ethe

aeAu

stra

lia

(Que

ensl

and)

8

Taua

la l

epid

usWanl

ess

1988

Astianae

Aust

rali

a (Q

ueen

slan

d)7

Thia

nia

bham

oens

isTh

orel

l 18

87Itatinae

Sing

apor

e5

Thor

elli

a en

sife

raThorell 1887

Spilarginae

Sing

apor

e5

b

Trit

e au

rico

maUrquhart 1885

Cyta

eina

eNe

w Ze

alan

d9

CTr

ite

plan

icep

sSimo

n 18

99Cy

taei

nae

New Zealand

10n

Tula

rosa

de L

esse

rt 1

925

plumosa

Hasariinae

Kenya

5b

Viciria praemandibul

aris

(Has

selt

189

3)Hyllinae

Sing

apor

e10

Zeno

doru

s or

bicu

latu

s(Keyserling 1881)

Euophrynae

Aust

rali

a (Q

ueen

slan

d)4

CNon-sa

ltic

ids

Cheiracanthium stratioticumL.

Koch 1873

Club

ioni

dae'

New

Zeal

and

8Cl

ubiona cambridge

iL.

Koch 1873

Club

ioni

dae'

New

Zeal

and

8Dysdera crocata C

.L.K

och 1838

Dysderidae'

New

Zeal

and

10

Supunn

a pi

cta

(L.K

och

1873

)Cl

ubio

nida

e'Ne

w Ze

alan

d8

Taieria erebus

(L.K

och

1873

)Gnaphosidae'

New

Zeal

and

7

374

Table 2.-Number of individuals tested (n) and percentage that captured flies (C) during tests usingblinded spiders in tubes. Species marked with a superscript 1 are non-salticids .

as the barrier was removed, and then left for24 h. At the end of tests, dead flies were in-spected for fang holes and mastication to con-firm that they had been bitten by the spider .

Statistical methods .-Tests of indepen-dence in 2X2 contingency tables were carriedout using Fisher's exact test, whereas tests inlarger tables were carried out using X 2 (ex-cluding species for which n < 10). Tests ofassociation were carried out using Spearman'srank correlations (excluding species for whichn < 10). McNemar's test for significance ofchanges (Sokal & Rohlf 1981) was used tocompare frequency data obtained from se-


quential testing of individuals in darkness andlight .

RESULTSSuccess at non-visual predation.-Each

of the 47 species tested (42 salticids and 5non-salticids) caught prey in the absence ofvisual cues in at least one type of test (Tables2-4) . There was no evidence of differencesamong salticid species in how frequently theycaught prey in darkness when blinded (in hor-izontal or vertical tubes) or when sighted andtested for 24 h (for all test types, P > 0.1) .However, there was significant variation

Tubes horizontal Tubes verticaln C n C

Tests using fruit fliesClubiona cambridgei' 9 66 6 66Bavia aericeps 12 17Corythalia canosa 9 22Cosmophasis micarioides 6 17Epeus sp . 1 7 14Euophrys parvula 12 33Hasarius adansoni 8 13Helpis minitabunda 8 24 -Holoplatys sp . 7 0 9 22Jacksonoides queenslandicus 10 0 14 14Lyssomanes viridis 10 0 11 9Marpissa marina 7 0 7 14Mopsus mormon 10 10Myrmarachne lupata 6 0 5 20Phidippus johnsoni 12 0 11 9Plexippus calcarata 11 27Portia labiata 7 0 8 13Tauala lepidus 6 17Thiania bhamoensis 7 14Trite auricoma 15 20Trite planiceps 10 40 7 43Zenodorus orbiculatus 6 17

Tests using house fliesClubiona cambridgei' 4 100Bavia aericeps 5 20Euophrys parvula 5 20 -Helpis minitabunda 4 0 5 20Jacksonoides queenslandicus 9 0 10 20Marpissa marina 8 38 7 14Mopsus mormon 4 25Phidippus johnsoni 5 0 10 10Tauala lepidus 7 43Trite auricoma 8 38Trite planiceps 10 40

TAYLOR ET AL. SALTICID NON-VISUAL PREY CAPTURE

375

among salticid species during tests usingsighted spiders in tubes (fruit flies, x2 = 95 .06,14 df P < 0.001; house flies, X2 = 103 .30, 17df P < 0.001) and tests using sighted spidersin petri dishes (house flies, X2 = 154.80, 13df P < 0.001). All species of non-salticidscaught flies in all types of test, and there wasno evidence that they differed in capture fre-quency in any type of test (for all test types,P > 0.1) .

In experiments testing individual spider'ssuccess at catching flies in darkness and inlight, all salticids caught fruit flies and houseflies less frequently in the dark than in thelight (Table 4). In contrast, there was no evi-dence that absence of light affected how oftenClubiona cambridgei, the non-salticid tested,caught flies (Table 4) .

Some sighted spiders caught flies immedi-ately following the first physical contact withthe flies ('immediate captures') . During testsin tubes using fruit flies as prey, immediatecaptures were made by the non-salticids Clu-biona cambridgei (16 of 24 captures record-ed), Dysdera crocata (2 of 10), Supunna picta(6 of 9) and Taieria erebus (4 of 8) as wellas the salticids Euophrys parvula (1 of 10),Helpis minitabunda (1 of 7), Mogrus dumi-cola (1 of 4) and Phidippus sp . 1 (1 of 5) ;during tests in tubes using house flies as prey,they were made by the non-salticids Cheira-canthium stratioticum (3 of 11), Clubionacambridgei (19 of 45), Dysdera crocata (2 of13), and Supunna picta (6 of 16) as well asthe salticids Corythalia canosa (1 of 5), Eu-ophrys parvula (1 of 18), Phidippus sp . 2 (1of 8), Portia africana (1 of 4) and Trite plan-iceps (5 of 18); during tests in petri dishesusing house flies as prey, the non-salticidsClubiona cambridgei (8 of 20), Dysdera cro-cata (3 of 10), and Supunna picta (4 of 15)made immediate captures, whereas Trite plan-iceps (9 of 37) was the only salticid observedto make immediate captures in these tests .

Associations amongst spider size, aggres-siveness and success at prey capture .-Sal-ticid species varied in the frequency withwhich they confronted fruit flies and houseflies when first contacted ('aggressiveness')during tests in tubes (fruit flies, X2 = 63 .20,13 df P < 0.001 ; house flies, X 2 = 79.34, 16df P < 0.001) and in petri dishes (house flies,X 2 = 109.40, 13 df, P < 0.001) (see Table 3) .In contrast, all of the non-salticids were sim-

ilar in that they usually confronted flies whenfirst contacted (see Table 3), and there was noevidence of species variation in frequency ofconfrontation by non-salticids during any testtype (for all test types, P > 0.1) .

Salticid species that often confronted flieswhen first contacted tended to catch flies morefrequently than species that rarely confrontedflies during tests of sighted spiders in tubes(fruit flies, r s = 0.6677, 13 df P < 0.01 ; houseflies, rs = 0.6779, 16 df P < 0.01) and testsof sighted spiders in petri dishes (house flies,rs = 0.5965, 13 df, P < 0.05) .

During tests with fruit flies in tubes, Triteauricoma individuals that confronted flieswere more likely to catch the prey than wereconspecifics that avoided flies when first con-tacted (P < 0.05) . For all other species in alltests, there was no evidence that likelihood ofcatching flies was related to an individual spi-der's response when first contacted (for allspecies in all test types, P > 0.1) . There wasno evidence of relationship between size ofsalticid species (Table 1) and the proportionof individuals that confronted or caught fliesin tests of sighted spiders in tubes or in petridishes using either prey type (for all test types,P > 0.1) .

Comparison of arenas used with sightedspiders .-For the following salticids, houseflies were captured less frequently in the petridish arena than in the tube arena (Table 3) :Cosmophasis sp . (P < 0.05), Euophrys par-vula (P < 0.001), Helpis minitabunda (P <0.001), Marpissa marina (P < 0 .001), Mopsusmormon (P < 0.05), Portia labiata (P <0.001), Portia shultzi (P < 0.05), Trite auri-coma (P < 0.01) and Trite planiceps (P <0.01). However, there was no evidence for anynon-salticid species that frequency of prey-capture by was different in these two types oftests (for all species, P > 0.1) .

Some salticids confronted house flies lessfrequently when tested in petri dishes ratherthan in tubes (Table 3) : Corythalia canosa (P< 0.05), Euophrys parvula (P < 0 .001), Mar-pissa marina (P < 0.001) and Portia labiata(P = 0 .057). However, there was no evidencefor any non-salticid species that frequency ofconfrontation was different in these two typesof test nor was there evidence that frequencyof contact with house flies was different inthese two types of test for any salticid or non-salticid (for all species, P > 0.1) .

376


Table 3 .-Behavior and prey-capture success of sighted spiders in tubes' and in petri dishes . Speciesmarked with a superscript 1 are non-salticids . `Contact' is the percentage of n that contacted the fly (seetext) . `Confront' is the percentage of individuals that confronted, rather than avoided, the fly (see text)immediately after first contact and `Capture' is the percentage of n that captured the fly .

n Contact Confront Capture

Tests in tubes using fruit flies as preyCheiracanthium stratioticum' 28 50 86 50Clubiona cambridgei' 33 73 92 73Dysdera crocata' 18 72 62 56Supunna picta' 15 73 82 60Taieria erebus' 16 63 70 50Bavia aericeps 15 73 9 0Corythalia canosa 17 53 0 12Cosmophasis bitaeniata 4 75 33 50Cosmophasis sp. 12 83 0 42Epeus sp . 2 3 67 0 0Eris marginata 5 100 0 0Euophrys parvula 22 64 57 45Helpis minitabunda 46 87 8 15Holoplatys planissima 8 50 25 0Jacksonoides queenslandicus 20 80 0 0Lyssomanes viridis 33 70 0 12Marpissa marina 28 93 23 46Mogrus dumicola 26 42 9 15Mopsus mormon 8 88 14 0Phidippus sp . 1 13 85 45 38Phidippus sp . 2 9 89 13 33Portia fimbriata 22 64 0 5Portia labiata 64 53 3 5Tauala lepidus 13 77 40 46Trite auricoma 38 53 25 18Trite planiceps 43 72 43 63Zenodorus orbiculatus 2 50 100 0

Tests in tubes using house flies as preyCheiracanthium stratioticum' 13 85 90 85Clubiona cambridgei' 54 93 89 83Dysdera crocata' 15 100 85 87Supunna picta' 18 100 88 89Bavia aericeps 15 100 7 13Corythalia canosa 17 94 38 29Cosmophasis sp . 16 88 14 38Epeus sp . 2 7 100 0 57Eris marginata 5 100 0 0Euophrys parvula 22 95 43 82Helpis minitabunda 50 100 6 34Holoplatys planissima 12 92 20 25Jacksonoides queenslandicus 16 94 7 0Lyssomanes viridis 42 98 3 14Marpissa marina 32 94 50 56Mogrus dumicola 26 96 28 46Mopsus mormon 10 80 0 40Phidippus sp . 1 14 100 38 100Phidippus sp . 2 9 100 13 89Portia africana 7 86 17 57Portia fimbriata 26 100 0 12Portia labiata 24 83 11 33Portia shultzi 10 100 20 50


Prey-capture behavior in the absence ofvisual cues.-Salticids always lunged to catchprey, and were never observed to leap ontoprey as they commonly do in light. No spider,salticid or non-salticid, ever lunged at the fliesprior to being touched . Cheiracanthium stra-tioticum and Clubiona cambridgei, non-salti-cids, sometimes chased after flies that movedaway following contact, but no salticid everdid this .

After lunging at flies, salticids sometimesheld the flies for 1-5 sec with their fangswhilst appearing to make little or no attemptat using their legs to grasp the fly. In theseinstances, flies broke free or were released bythe spiders but always stopped moving within10 min of being bitten. During tests usingsighted spiders in tubes, the following salti-cids made bite-then-release attacks on houseflies : Bavia aericeps (1 of 2 captures record-ed), Corythalia canosa (1 of 5), Helpisminitabunda (1 of 17 ), Mogrus dumicola (2of 12), Mopsus mormon (1 of 4), Phidippussp. 1 (2 of 14), Portia labiata (1 of 8), Triteauricoma (3 of 9) and Trite planiceps (2 of18). After these attacks, spiders usually later

Table 3.-Continued.

377

picked up the immobilized fly and ate it, theonly exception being Bavia aericeps. Triteplaniceps was the only salticid observed tokill a fruit fly by a bite-then-release attack (3of 27) . During tests in petri-dish arenas usinghouse flies as prey, spiders that grasped fliesalways held onto them until they died .

DISCUSSION

Salticids are conventionally thought of asstrictly diurnal hunters that shelter overnight,and this general impression is supported byobservations of spider activity patterns in na-ture and in the laboratory (e .g ., Jackson 1976 ;Givens 1978; Taylor 1997). Nonetheless, thepresent study finds that, as well as being ex-traordinarily adept visual predators (Forster1977, 1979 ; Jackson & Pollard 1996; Bear &Hasson 1997), salticids are able to coordinateattacks using other senses when visual cuesare unavailable . This finding in a laboratorycontext establishes a need for research inves-tigating naturally occurring situations duringwhich salticids might depend primarily orsolely on cues other than vision to coordinateattacks .

n Contact Confront Capture

Tauala lepidus 16 100 19 25Trite auricoma 33 91 21 27Trite planiceps 21 100 70 86

Tests in petri dishes using house flies as preyClubiona cambridgei' 22 91 85 91Dysdera crocata' 12 100 67 83Supunna pitta' 16 94 87 94Bavia aericeps 15 93 0 0Corythalia canosa 15 87 0 7Cosmophasis sp . 14 86 8 0Epeus sp. 9 89 0 11Euophrys parvula 46 85 0 0Helpis minitabunda 39 95 5 3Holoplatys planissima 4 100 0 0Jacksonoides queenslandicus 20 85 0 0Lyssomanes viridis 35 94 0 9Marpissa marina 26 100 4 4Mopsus mormon 12 83 0 0Portia africana 5 100 0 0Portia labiata 66 89 0 0Portia shultzi 10 100 0 0Tauala lepidus 12 83 20 17Trite auricoma 36 92 9 3Trite planiceps 70 90 44 53

378


Table 4.-Number of spiders that caught flies in light vs . dark. Species marked with a superscript 1 arenon-salticids . Only columns `Light only' and `Dark only' are relevant for McNemar tests for significanceof changes (Sokal & Rohlf 1981) .

Lightonly

Darkonly Both Neither

McNemartest

Tests using fruit fliesClubiona cambridgeii 2 3 10 3 NSAsemonea tenuipes 7 0 2 1 P < 0.01Bavia aericeps 15 0 1 2 P < 0.001Corythalia canosa 10 0 1 4 P < 0.005Cosmophasis micarioides 14 0 2 3 P < 0.001Cosmophasis bitaeniata 5 0 2 4 P < 0.05Cyrba ocellata 6 0 1 3 P < 0.025Euophrys parvula 17 0 3 5 P < 0.001Epeus sp. 2 18 0 1 2 P < 0.001Eris marginata 11 0 4 0 P < 0.001Euryattus sp . 9 0 3 4 P < 0 .005Hasarius adansoni 13 1 3 3 P < 0.005Helpis minitabunda 17 1 2 2 P < 0.001Hentzia mitrata 5 0 2 1 P < 0.05Holoplatys sp . 19 0 4 3 P < 0.001Jacksonoides queenslandicus 20 0 4 4 P < 0.001Lyssomanes viridis 15 0 0 4 P < 0.001Marpissa marina 18 1 2 3 P < 0.001Menemerus bivattatus 12 0 3 5 P < 0.001Mopsus mormon 13 0 2 5 P < 0.001Myrmarachne lupata 19 1 3 2 P < 0.001Natta rufopicta 14 1 2 3 P < 0.001Phidippus johnsoni 18 0 0 3 P < 0.001Plexippus calcarata 17 0 3 1 P < 0.001Portia labiata 9 2 0 11 P < 0.05Sirnaetha paetula 19 0 3 1 P < 0.001Tauala lepidus 12 1 3 1 P < 0.005Thiania bhamoensis 22 1 2 2 P < 0.001Thorellia ensifera 11 1 2 2 P < 0.005Trite auricoma 19 0 6 1 P < 0.001Trite planiceps 16 0 8 1 P < 0.001Tularosa plumosa 5 0 2 2 P < 0.05Viciria praemandibularis 13 0 3 4 P < 0.001Zenodorus orbiculatus 15 0 1 3 P < 0.001

Tests using house fliesClubiona cambridgei' 0 2 5 1 NSBavia aericeps 8 0 2 0 P < 0.005Euophrys parvula 5 0 2 1 P < 0.05Helpis minitabunda 7 1 0 6 P < 0.05Jacksonoides queenslandicus 8 0 1 1 P < 0.005Marpissa marina 9 0 2 0 P < 0.005Mopsus mormon 5 0 2 0 P < 0.05Phidippus johnsoni 8 0 2 1 P < 0.005Plexippus calcarata 6 0 1 1 P < 0.025Tauala lepidus 5 0 2 0 P < 0.05Trite auricoma 4 0 1 3 P < 0.05Trite planiceps 8 0 4 0 P < 0.005


379

Acute vision is not a prerequisite for suc-cessful cursorial hunters . Many spiders fromother families (i .e ., non-salticids) are success-ful cursorial hunters despite lacking acute vi-sion (e.g ., Ctenidae, Pisauridae, Clubionidae,Gnaphosidae) and there is no obvious reasonto presume that salticids could not also some-times hunt cursorially when visual cues arenot available. There is even anecdotal evi-dence that at least one salticid, Phidippus otio-sus (Hentz 1846) [= Phidippus pulcher (Wal-ckenaer 1837)], does sometimes hunt afternightfall (Reiskind 1982) . Web-building spi-ders from other families lack acute vision, andinstead use their webs as extensions of theirtactile sense organs to hunt both during theday and at night (Witt 1975 ; Suter 1978 ; Jar-man & Jackson 1986) . Web-building salticidshave at their disposal all of the prey-catchingfacilities used by web-builders from otherfamilies but whether salticids make use ofthese facilities when visual cues are absent isnot known . Salticids that build webs (Jackson& Hallas 1986 ; Jackson & Pollard 1990) orweb-like nests (Hallas & Jackson 1986a, b ;Jackson & McNab 1989a) are prime candi-dates for investigation of nocturnal predation .

Although predation is conventionally envis-aged as a means of gaining food, it may alsofunction as defense (Curio 1976 ; Archer1988). Salticids may commonly find them-selves in situations that demand immediate re-sponses to attacks in the absence of visualcues from the attacker. For example, salticidsmay be suddenly attacked by fast-movingpredators in light (Jackson 1980 ; Young &Lockley 1987 ; Jackson & McNab 1989b ;Jackson et al . 1990), in darkness when in theirnests at night (Jackson 1976 ; Jackson & Gris-wold 1979 ; Jarman & Jackson 1986 ; Taylor1997) or in dark places during the day. Ad-ditionally, salticids attacked in their nests dur-ing the day may be denied visual cues by theopaque walls of their nest (see Hallas & Jack-son 1986b) . How salticids mediate anti-pred-ator behavior in these contexts has not yetbeen studied specifically, but immediate ori-entation and attack (similar to confrontationand `immediate captures' in our experiments)might be an appropriate defense against an un-identified intruder.

The poorly known natural histories of mostsalticid species cause difficulty in interpretingthe observed species differences in predation

success and aggressiveness toward flies in theabsence of visual cues. Nonetheless, results ofthis laboratory study do suggest certain hy-potheses about how salticids might respond innature. For example, tendency to respond ag-gressively when touched by flies in darknesswas not strongly associated with size, a mea-sure of physical ability . Instead, we may con-sider each species' relationships with prey andenemies to understand why salticids varied inaggressiveness. Most likely, success in naturedepends not only on a salticid's size orstrength, but also on the types of predators andprey encountered and the situations in whichencounters take place. For example, somelarge salticids may have responded timidly be-cause their nocturnal predators are especiallyferocious or encounters take place at siteswhere -escape is easy, whereas some smallersalticids may have responded aggressively be-cause their nocturnal intruders are less dan-gerous or because encounters with enemies innature are difficult to escape .

Some salticids (e .g., Euophrys parvula,Marpissa marina), adjusted their tendency toconfront and later catch flies in darkness de-pending on ease of avoidance . These speciesmade greater use of the comparatively easyavoidance option when tested in expansive pe-tri dishes, but they responded more aggres-sively when in tubes with few options for es-cape. If prey-capture was based on feedingconsiderations, then we would not have ex-pected these differences . Instead, evasion ofpotential enemies, rather than hunting, seemsa better explanation of non-visual predationby these salticids in our experiments .

Trite planiceps, the salticid for which non-visual predation was first reported by Forster(1982), appears to be a special case . Althoughother salticids often caught house flies whentested in tubes, T. planiceps was unusually ag-gressive and successful at prey-capture whentested in the more spacious petri-dishes . Per-haps, as was suggested by Forster (1982), T.planiceps' unusual aggressiveness is an ad-aptation related to frequent encounters withpotential prey, dangerous intruders, or both inthe restrictive dark recesses within rolled-upleaves where this species normally lives . Triteplaniceps used in the present study share theirhabitat with each of the non-salticids tested .Of these, Clubiona cambridgei, Cheiracan-thium stratioticum and Taieria erebus have

380

been observed eating Trite planiceps adults,juveniles and eggs in nature (PWT unpubl .data). Of course, other salticids tested also en-counter enemies in darkness (Jackson 1976 ;Jarman & Jackson 1986), but the abundanceof nocturnal hunting spiders and confining mi-crohabitat inside rolled-up leaves may makeencounters with predators unusually frequentand unusually difficult to escape .

ACKNOWLEDGMENTS

Financial support was provided by a NewZealand Universities Post-graduate Scholar-ship to PWT, grants from the Marsden Fundof New Zealand (UOC512), the National Geo-graphic Society (2330-81, 3226-85, 4935-92) and United States National Science Foun-dation (BNS 8617078) to RRJ, and a ClemsonUniversity Graduate School Scholarship toMWR. Malcolm Williamson collected andsent Helpis minitabunda from Auckland, NewZealand. We thank New Zealand Ministry ofAgriculture and Fisheries for import permits .

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Manuscript received 12 May 1997, revised 1 June1998.

prey-capture by jumping spiders - american arachnological society

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