Cooperative Prey Capture in the Communal Web Spider, Philoponella Raffrayi (Araneae, Uloboridae)

5 Pages·1998·3.6 MB·English

by  Toshiya Masumoto

1998. The Journal of Arachnology 26:392-396
RESEARCH NOTE
COOPERATIVE PREY CAPTURE IN THE COMMUNAL
WEB SPIDER, PHILOPONELLA RAFFRAYI
(ARANEAE, ULOBORIDAE)
Prey capture advantage has played an im- building spider that occupies the tropical rain
portant role in the evolution of communal or forest undergrowth of peninsular Malaysia
social spiders (Shear 1970; Rypstra 1985, (Simon 1891; Masumoto 1992). I studied this
1986; Buskirk 1981; Uetz 1986, 1989). Com- species in the Pasoh Forest Reserve in Negri
munal web organization may improve prey Sembilan state, Malaysia. A colony ofP, raf-
capture in two ways: 1) it may improve the frayi is composed ofindividual orb-webs con-
ability ofwebs to interceptprey (the “ricochet nected to one another by non-adhesive silk.
effect”) (Uetz 1989), and 2) it opens the pos- All uloborids lackpoison glands andmustrely
sibility ofcommunal prey immobilization that on wrapping to subdue prey (Lubin 1986).
may allow spiders to capture larger and pre- The average body length of this species is
sumably more profitable prey. Communalcap- 6.21 mm in females and 3.15 mm in males
ture of large insect prey has been observed in (Masumoto 1992). The volume of colonies is
a number of social web-building spiders, such variable according to the number of individ-
as Agelena consociata Denis 1965 (Krafft uals in the colony (Table 1). The age of adult
1969), Anelosimus eximius (Keyserling 1884) females is easily determined by their body
(Vollrath & Rohde-Arndt 1983; Christenson color. Adult females are orange for at least a
1984; Pasque & Krafft 1992), Mallos gregalis week after the final molt, becoming black a
(Simon 1909) (see Jackson 1979), and it has few weeks later.
been demonstrated that communal spiders I conducted field observations in a 2 ha re-
capture larger prey than solitary spiders (Bus- search area from February-April 1992 and
kirk 1981; Nentwig 1985; Uetz 1986). also in March 1993. All colonies found within
Members of the genus Philoponella Mello- this area were included in the study. To locate
Leitao are known to construct communal these colonies, I searched within the study
webs, but most have been reported to employ area for 3 days before the 25 February and the
only non-cooperative prey capture (see Bur- 17 March study periods. All observations
gess 1978; Buskirk 1981; Smith 1982; Lubin were made between 0800-1800 h, which cor-
1986). However, cooperative prey capture has responded to the daylight periods in this area.
been reported in a few species ofPhiloponella I recorded the number, stage ofmaturation and
&
(see Breitwisch 1989; Binford Rypstra behavior ofspiders in colonies on 25 February
1992). To understand the diversity of coop- and 17 March 1992. In March 1993, I also
erative prey capture and social behavior in the conducted a total of 17 hours of field obser-
genus Philoponella, the prey capture behavior vations on the only colony (46339) still pres-
of as many species as possible should be de- ent in the study area. For this colony, I re-
scribed. corded the stage of maturation, relative body
This study describes the colony composi- length of interacting individuals and each in-
tion and prey capture handling behavior ofthe sect that entered the colonial web. Individuals
uloborid spider Philoponella rajfrayi (Simon were not marked and the relative body length
1891) and determines if the efficiency with between the spider and the insect prey was
which they capture large insects is higher estimated by eye. I collected females and their
when spiders hunting cooperatively than when egg sacs from the No. 2 colony described be-
they hunt singly. low. I preserved them in 70% alcohol and
Philoponella rajfrayi is a communal web- counted the number of eggs per egg sac and.
392
MASUMOTO—COOPERATIVE PREY CAPTURE 393
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394 THE JOURNAL OF ARACHNOLOGY
—
Table 2. The number of prey entering the col- 1 40n
ony, captured or not captured, in a colony of Phil-
oponella raffrayi. Relative prey size is the ratio of
prey body length to spider body length. 0w) 1 30 t
CR
UJ
Relative t
prey size 1 20
(prey/ Cooper-
spider) Single ative
<0.1 Success 30 1 1 10
Fail 1 0
Efficiency (%) 97 100
0.1-0.5 Success 32 2 —
Fail 4 0 1001.3 1.4 1.I5 1.6 1.7 1.8
Efficiency (%) 89 100
0.5-1.0 Success 1 4 Cephalothorax Width (mm)
Fail 11 0 —
Efficiency (%) 8 100 Figure 1. The correlation between the cepha-
1.0< Success 0 0 lothorax width of females and the number of eggs
deposited. Spearman’srankcorrelation: Rs = 0.523,
EFafifliciency (%) 06 —0 n = 15. P = 0.046.
April in 1992, and he juveniles remained in
under abinocularmicroscope, measured to the the same colony where they had hatched. De-
mm
nearest 0.1 the width of females’ cepha- velopmental stages of females were synchro-
lothorax. Two of them were deposited as nous within the same colony, but not synchro-
voucher specimens in the collection ofthe De- nous among different colonies. Furthermore,
partment of Zoology, National Science Mu- the number ofspiders in the same colony nev-
seum, Tokyo (NMST-Ar 3514, 3525). Capture er increased, and no fusion of colonies was
efficiency is defined as the ratio ofthe number observed. During April, no colonies remained
of insects captured compared to the number at the same web site and three colonies, each
of insects entering the webs. containing more than 100juvenile P. raffrayi,
I observed eight colonies in February and appeared at different web sites. All adult fe-
ten colonies in March 1992 (Table 1). Each males disappeared from the juvenile web col-
colony consisted of members of a similar de- ony, and I could detect no parent-offspring in-
velopmental stage, apparently representing teraction except for egg sac guarding.
only variation in size of the same instar. Be- Furthermore, Argyrodes and Portia were
tween 25 February-17 March (3 weeks), six found in the colonies.
of the eight colonies remained at the same During the observation, I recorded 92 in-
web site, but two colonies disappeared from sects of four orders entering webs; Diptera
the study area and four colonies newly ap- (75), Hymenoptera (15), Coleoptera (1), Lep-
peared. In March 1992, females of No. 2 col- idoptera (1 larva). Ofthese insects, the spiders
ony produced twig-like egg sacs, hung them captured 66 Diptera, two Hymenoptera, one
from the hub and began guarding the eggs. Coleoptera and one larva of Lepidoptera.
The mean number of eggs per egg sac was Wrapping was dominantly conducted by in-
118 ±9.96 (x ±SD, n = 15). This value was dividual females. However, when prey was
correlated with the cephalothorax width of its trapped in the periphery of an individual orb
mother (Spearman’s rank correlation; Rs = web, 7 out of 70 prey items (10%) were
0.523, n = \5, P = 0.046; Fig. 1). However, wrapped by two cooperating females. They
8 of 13 females measured had a cephalothorax first subdued prey by throwing silk on it from
mm
width of 1.5 but produced 101-132 eggs. a distance and began to more tightly wrap
Factors that may have contributed to the dif- prey cooperatively as they rotated it. The prey
ference would be energy gain during the adult capture efficiency ofa single females was 89-
stage. Oviposition occurred between March- 97% when prey size was less than the halfthe
MASUMOTO—COOPERATIVE PRE’^CAPTURE 395
body length of the spider, but this decreased Burgess, J.W. 1978. Social behavior in group-liv-
to only 8% when the relative prey size was ing spider species. Symp. Zool. Soc. London.,
between 0.5-1, and no prey was captured 42:69-78.
when the prey length was greater than spider Buskirk, R.E. 1981. Sociality intheArachnida, Pp.
body length. However, cooperative prey cap- 281-367. In Social Insects. Vol. II (H.R. Her-
ture by two females resulted in 31% prey cap- Chrmiasntenn,soend.,).TAEc.ad1e9m8i4.c PBreeshsa,viLoorndoofn,coNloenwialYoarnk.d
ture efficiency when the relative prey size was
solitary spiders of the theridiid species Anelosi-
between 0.5-1 spider length, which was high- mus eximius. Anim. Behav., 32:725—734.
er than that by a single female (Fisher’s exact Jackson, R.R. 1979. Predatory behavior ofthe so-
probability = 0.0027; Table 2). Even in cases cial spiderMallos gregalis: Is it cooperative?In-
where two females caught prey cooperatively, sectes Sociaux, 26:300- -312.
only one female fed on the prey item. In six Krafft, B. 1969. Various aspects of the biology of
out of seven cases, females that were larger Agelena consociata Denis when bred in the lab-
by 10% of body length and more matured fe- oratory. American Zool., 9:201-210.
males fed alone on the captured prey. The ef- Lubin, YD. & R.H. Crozier. 1985. Electorophor-
fect of web ownership on the advantage in etic evidence for population differentiation in a
taking over a prey could not determined be- social spiderAchaearanea wau (Theridiidae). In-
cause I could not discrinunate the owner from Lubsienc,teYsDS.oci1a9u8x6,.32W:e2b97b-u3i0l4d.ing and prey capture
the intruder.
in Uloboridae, Pp. 132-170. In Spiders: Webs,
Communal uloborid spiders, such as Phil- Behavior, and Evolution.(W.A. Shear, ed.). Stan-
oponella oweni Chamberlin 1924 were
ford Univ. Press, California.
thought to lack any cooperative prey capture Masumoto, T. 1992. The composition of a colony
behavior (Buskirk 1981). However, coopera- of Philoponella rajfrayi (Uloboridae) in Penin-
tive prey capture has since been reported in a sular Malaysia. Acta ArachnoL, 41:1-4.
species of Philoponella in the Cameroon Nentwig, W. 1985. Social spiders catchlargerprey:
(Breitwisch 1989), and for P. republicana a study ofAnelosimus eximius (Araneae: Theri-
Simon 1891 (see Binford & Rypstra 1992). diidae). Behav. Ecol. SociobioL, 17:79-85.
The prey capture by P. rajfrayi is similar to Pasquet, A. & B. Krafft. 1992. Cooperation and
that of P. republicana, except that no more prey capture efficiency in a social spiderAnelo-
than two individuals were observed to share simus eximius (Araneae, Theridiidae). Ethology,
90:121-133.
itnhertehismabyehasveivoerr.alThtyepsees roefsucltosopeinrdaitciavtee ptrheayt Roeloffs, R. & S.E. Riechert. 1988. Dispersal and
population-genetic structure of the cooperative
capture in the genus Philoponella.
spider,Agelena consociata, inWestAfricanrain-
I am indebted to J. Intachat for generous forest. Evolution., 42:173-183.
permission to use the laboratory in Forest Re- Rypstra, A.L. 1985. Aggregation of Nephila cla-
search Institute of Malaysia. I thank Y. Ono, vipes (L.) (Araneae: Araneidae) in relation to
Y. Tsubaki and A. Furukawa for encourage- prey availability. J. Arachnol., 13:71-78.
ment. I am indebted to M. Yoshida, T. Mi- Rypstra, A.L. 1986. High prey abundance and a
yashita, B.D. Opell and two anonymous re- reduction in cannibalism: the first step to soci-
viewers for reading manuscript and making ality in spiders (Arachnida). J. Arachnol., 14:
helpful suggestions. I thank T. Kamura and N. 193-200.
Ono for their kind advice on the deposition of Shear, WA. 1970. Theevolutionofsocialphenom-
voucher specimens. This study was partly sup- ena in spiders. Bull. British Arachnol. Soc., 1:
ported by a Grant from Global Environmental 65-76.
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