This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Behavioral Ecology Vol. 10 No. 2: 115–121 Previous foraging success inﬂuences web
building in the spider Stegodyphus lineatus
Alain Pasquet,a Raymond Leborgne,a and Yael Lubinb
Laboratoire de Biologie et Physiologie du Comportement, URA CNRS n 1293, UHP Nancy 1, B.P.
239, 54506 Vandoeuvre les Nancy Cedex, France, and bMitrani Center for Desert Ecology, Blaustein
Institute for Desert Research, Ben Gurion University, Sede Boker Campus, 84993 Israel
a Stegodyphus lineatus (Eresidae) is a desert spider that builds an aerial capture web on bushes in the Negev desert in southern
Israel. Web building for spiders is costly in energy, time, and risk of predation. Spiders should trade-off these costs with the
beneﬁts in terms of prey capture. We tested the hypothesis that the previous foraging success of the spider inﬂuences the effort
invested in foraging. Speciﬁcally, we asked whether an increase in food intake causes spiders to reduce web renewal activity and
web size. Alternatively, time constraints on foraging and development, resulting from a short growing season, could induce
spiders to continue foraging even when supplemented with prey. The cost of web building was measured as time and mass loss.
To build an average size web (about 150 cm2), we calculated that a spider requires 6 h and that spiders lose 3%–7% of their
weight. In ﬁeld experiments, spiders responded differently to food supplementation in 2 different years. In 1994, they improved
their condition compared to individuals whose webs were removed to reduce foraging opportunities and compared to control
spiders. In 1995, spiders tested earlier in the season than the previous year did not improve their condition in response to prey
supplementation. Nonetheless, in both years, food-supplemented spiders built signiﬁcantly smaller webs than food-deprived and
control spiders. This result was conﬁrmed in a laboratory experiment where prey intake was controlled. We conclude that for
S. lineatus immediate foraging risks outweigh the potential time constraints on foraging. Key words: Eresidae, food supplementation, optimal foraging, spiders, Stegodyphus lineatus, web building. [Behav Ecol 10:115–121 (1999)] F oraging effort can be viewed as a compromise between the
energetic needs of the individual for maintenance,
growth, and reproduction and the costs or risks associated
with foraging activity (Lima and Dill, 1990). The beneﬁts of
foraging are frequently traded off against costs, which may
vary in accordance with the condition or ‘‘state’’ of the forager (Krebs and Kacelnik, 1991). These foraging trade-offs
provide a fertile ﬁeld for investigating decision-making processes in animals and, in particular, the ways that conﬂicts are
resolved between competing requirements over different time
scales—for example, over the time scale of a foraging bout
versus the time scale of the forager’s life span.
For web-building spiders, foraging costs associated with the
capture web include the energy required to construct and
maintain the web (silk production and costs of activity) and
the risks associated with being exposed while active on the
web (Lubin, 1973; Uetz, 1992). The beneﬁt from building a
web is derived from prey caught in the web. The presence of
an effective capture web determines the spider’s energy budget in the short term. Thus, the decision to build a web is a
foraging decision, which, in the context of optimal foraging
theory, should be sensitive to the expected ratio of beneﬁts
to costs summed over the duration of the web (Higgins, 1990;
Higgins and Buskirk, 1992; Riechert and Luczak, 1982). The
web-building process is repeated at intervals during the spider’s lifetime, and the number of webs built during the lifetime varies among species. In some species new webs are constructed daily, while in others both the frequency and the extent of web renewal are more variable (Eberhard, 1986; LuAddress correspondence to A. Pasquet. E-mail: pasquet@scbiol.
Received 24 February 1998; accepted 1 June 1998.
1999 International Society for Behavioral Ecology bin, 1986; Tanaka, 1989). Because web-building is costly, each
web-building decision can have important consequences for
the spider’s lifetime success.
The beneﬁt and the cost to a spider of building and maintaining a web are inﬂuenced by three main factors: (1) the
spider’s energetic needs for maintenance and reproduction,
which will vary with its developmental stage—for example,
during moulting or egg maturation (Higgins, 1995; Vollrath,
1987), (2) abiotic and biotic environmental conditions (e.g.,
wind: Eberhard, 1971; Henschel and Lubin, 1992; prey availability: Pasquet et al., 1994; competition with other individuals: Leborgne and Pasquet, 1987; Ward and Lubin, 1992), and
(3) the individual’s immediate condition or internal state (Lubin and Henschel, 1996; Witt et al., 1968). Condition is a function of the spider’s previous foraging success (i.e., the ratio of
beneﬁts to costs obtained from previous webs). Decisions regarding web construction may be strongly inﬂuenced by condition: the marginal value of prey capture, and thus of web
renewal, is greater for a hungry spider than for a well-fed
individual, but the marginal cost of web renewal may also be
greater. Will an individual in poor condition be more likely
to accept the costs of web renewal? Will a spider in good condition show a more conservative strategy?
Some studies of foraging in spiders showed that well-fed
spiders reduced their investment in web construction (Higgins, 1990; Lubin and Henschel, 1996; Sherman, 1994). Foodsupplemented female orb-weaving spiders (Larinioides cornutus, Araneidae) switched from foraging to reproduction
(Sherman, 1994), whereas in a desert spider (Seothyra henscheli, Eresidae), well-fed individuals avoided the risks of predation and desiccation by remaining in their burrows (Lubin
and Henschel, 1996). In both instances, foraging appeared to
be traded off against other activities (reproduction or protection), and the outcome of the trade-off was inﬂuenced by the
individual’s condition. Behavioral Ecology Vol. 10 No. 2 116 Do other activities always take precedence over foraging
when an individual is well-fed, or are there situations in which
foraging activity will be maintained in spite of decreased marginal beneﬁts to the individual? The beneﬁts of continued
foraging should be greater if there is a time constraint on
growth. For example, if the food resource or other conditions
essential for development are present only during a limited
time period, continuous foraging will allow maximal utilization of these resources. We predict this to occur in species
that have an annual life cycle and a short ‘‘growing season,’’
limited, for example, by the timing of insect activity, as might
be the case in strongly seasonal habitats.
In the present study, we examined the inﬂuence of previous
foraging success on the decision to build a web in a desert
spider, Stegodyphus lineatus (Eresidae). The capture web of S.
lineatus is orblike in structure, with sticky, cribellate-silk lines
connecting nonsticky lines that radiate out from a tubular silk
retreat (Henschel et al., 1992; Ward and Lubin, 1993). The
web captures mainly ﬂying insects that strike the surface, become entangled in the sticky silk, and are pulled into the nest
by the spider. Stegodyphus lineatus does not renew its web daily, and frequently renews only a part of the surface, or enlarges the web by adding cribellate silk to existing nonsticky
threads (Pasquet et al., personal observations). When the web
is renewed, the old silk is discarded, and this energy investment is lost to the spider.
In the Negev desert, the life cycle of S. lineatus is generally
annual, and most of the growth to maturity occurs during 2–
3 months in the spring (March–May), when ﬂying insects are
most abundant (Schneider, 1995, 1996; Ward and Lubin,
1993). The energetic demands are greatest during this period
of growth to maturation. Spiders that do not reach maturity
during the spring have a low probability of surviving to reproduce the following year. Thus, in S. lineatus, the limited duration of high prey availability may be expected to select for
foraging behavior that will maximize prey capture opportunities independent of body condition.
We used an experimental approach on natural populations
in the ﬁeld and on spiders in captivity to ask whether the
spider’s feeding state affects its decision to renew the web.
Food availability was manipulated to create one group of wellfed individuals and another of food-deprived spiders, while
unmanipulated spiders provided a control for changes in behavior that might result from other environmental factors.
The energetic cost of web building was measured in terms of
the loss of body mass after the construction of a new web and
the time to produce a capture web. The decision to rebuild a
web was assessed by the number of new webs constructed in
each group and their sizes; body condition was assessed at the
beginning and end of the experiment. We predicted that spiders foraging in a condition-dependent manner should reduce web building when well fed; alternatively, if long-term
growth constraints inﬂuence foraging decisions, spiders
should maintain active webs even when they are well fed.
The study was conducted during March and April of 1994 and
1995 in the Negev desert in southern Israel. The study sites
were in two wadis (dry stream beds) separated by approximately 5 km. The wadis are grazed intensively by sheep, goats,
and camels, and the vegetation is sparse, consisting mainly of
dwarf shrubs (Artemisia herba-alba, Zygophyllum dumosum,
Hammada scoparia), spiny or aromatic annuals (Centaurea
spp.), and scattered, small trees (Thymelea hirsuta, Retama retaem). The spider builds a silken tubelike nest (retreat), incorporating plant material and prey remains and attached to
branches of shrubs. Nests frequently occur in the tops of the shrubs, but they may also be at ground level (Henschel et al.,
1992) and are often aggregated (Lubin et al., 1998). At the
beginning of March, most spiders were subadult or juvenile
and by the end of April some had already reached adult stage.
Web and spider parameters
The web of S. lineatus is composed of one or more (two to
four) two-dimensional surfaces: the general form is a rectangle or a triangle with the nest tube at one end (Ward and
Lubin, 1993). To obtain an estimate of web area, we measured
the length and width of a rectangular surface and the height
and base of a triangular surface: web size was calculated as
the sum of the areas of the different surfaces. In some cases
the spider had no capture web, but had spun some cribellate
threads around the entrance of the nest tube. Such threads
could occasionally trap insect prey; however, in most instances
its function appears to be protection against predators or ants.
We did not regard these cribellate threads as foraging webs,
and they were not included in the web measurements.
Spider size was determined by the total length of the body
including the abdomen and cephalothorax (LGTH) and by
the width of the cephalothorax (CTW). For spiders, the ﬁrst
measure is correlated with the amount of food ingested, and
the second is a measure of the stage of development (Lubin
et al., 1991; Vollrath, 1988). In S. lineatus, total body length
is positively correlated with body mass (Ward and Lubin,
1993). The residuals of regressions of LGTH or mass on CTW
provide a measure of body condition independent of size ( Jakob et al., 1996; Ward and Lubin 1993).
In 1994, 171 spiders were measured and individually
marked in two wadis (wadi 1: 114, wadi 2: 57), and in 1995
we marked and measured 137 spiders. The spiders in the 1994
population were signiﬁcantly larger than in 1995, both in
cephalothorax width (CTW) and in total length (LGTH)
SD, CTW 1994: 3.03
0.76 mm; CTW 1995: 2.65
0.63 mm, Mann-Whitney U
LGTH 1994: 11.1
2.46 mm; LGTH 1995: 10.1
.001). This difference was due to
the fact that observations were begun earlier in the season in
In both years, there was a signiﬁcant positive correlation
between web area and spider size (see also Ward and Lubin,
1992): larger spiders built larger webs (Pearson correlation of
log-transformed web area with LGTH, 1994: r
.001; 1995: r
Cost of web building
Duration of web building
The cost of an activity can be assessed as the relative amount
of time spent in the activity. Web-building time was studied
under standardized conditions (temperature 22 C, humidity
50%) in the C.N.R.S. laboratory at the University of Nancy.
The spiders were brought from the Negev and were kept in
boxes (16 9 8 cm) where they were fed twice a week with
cricket nymphs. For the observations of web building, the spiders were transferred with their nests to larger cages (50
10 cm), and each nest was tied to a wire mesh in the
center of the cage. The spiders were active at night, so observations of building behavior were made in the dark with a red
light. Web building can be divided into two stages: ﬁrst, construction of radii and nonsticky silk supporting-lines and second, construction of the sticky, cribellate silk. In the laboratory, the spiders built complete webs over a period of several
days and web sizes differed from one spider to another.
We deﬁned the speed of building the radii as the mean
speed (mm/s) for seven bouts of different lengths and the Pasquet et al. • Web building and foraging success in a desert spider 117 speed of laying cribellate silk of known length as equal to the
mean of four bouts. As webs were of different sizes, we standardized these results by focusing in each web on a surface
of 12 cm2 (an area equal to the smallest web built in the
laboratory). The total length of radii and cribellate silk was
measured in this area, and we obtained the total mean length
of the radii and cribellate silk for this determined surface. By
multiplying this length by the average speed, we obtained the
time required for S. lineatus to build 12 cm2 of web. the two study sites in 1994. In 1995, only one wadi was used
for the experiment. In both years, we used only adult and
subadult females and eliminated from the data analysis any
individuals that moulted during the experiment or that disappeared or moved to a new web-site. Loss of body mass
The cost of web construction was assessed by weighing spiders
before and after web building to obtain the mass lost after
constructing a web (Henschel and Lubin, 1992). The spiders
for this experiment were collected in the Municipal Zoo of
Beer Sheva (50 km north of Sede Boker) and removed together with their nest tubes. The nests were attached to chicken-wire fences (about 12 m long and 2 m high) which were
inside a screened insectary (14
3 m) in Sede Boker.
The spiders build webs readily on the wire mesh (Schneider
and Lubin, 1996), and the enclosure prevented entrance of
prey, parasites, or predators.
Before installation on the fence, we weighed and measured
each spider. After 24 h, the spiders were removed and
weighed again. Some had built a functional web, while others
constructed only nonsticky radii or no silk at all. Functional
webs were measured, and we compared the difference in mass
lost between spiders with or without a functional web. To obtain an estimate of body mass loss under resting conditions
(i.e., no construction activity), another group of spiders was
acclimated to the fence for 2–4 weeks and allowed to build
webs; we weighed the spiders on 2 consecutive days and noted
whether they had built new webs.
Inﬂuence of previous feeding on web building
To study the inﬂuence of the spider’s condition on its webbuilding decisions, we used the following experimental design: on the ﬁrst day, all the spiders found were measured
(total length and cephalothorax width) and marked for individual recognition with a dot of acrylic paint. We measured
web size (see above) and removed all of the webs (removing
silk attachments to branches, radii, and sticky spiral threads).
The following day, we measured the new webs that were constructed overnight and for the following experiment we used
only those spiders that had built new webs, with the rationale
that these individuals would be in a similar initial state. Spiders were assigned randomly to three groups: one group
which was not manipulated (control group), another in which
we removed the web (web-removal group), and a third in
which we removed the web after feeding the spiders with prey
(prey-supplemented group). Removing the web in the morning reduced the time available for foraging, as spiders could
renew the web only during the following night and foraging
occurs both during the day and night. We used ﬂour beetles
(Tenebrio molitor) of about 100 mg as prey, which are a relatively large meal for these spiders. This procedure was repeated every other day over the next 8 days (i.e., four webremoval and feeding manipulations). Each day we noted the
presence of the spider and web and measured web size. During daily monitoring of nests, we noted if spiders had moulted, moved to a new site, or if there were males, predators, or
ants in the nest or on the web. On the ﬁnal day of the experiment (day 9) we monitored spider presence and web size
and then removed the spiders from their nests and measured
their body size.
The same experimental procedure was repeated in each of Laboratory experiment
A similar experiment on spiders in captivity (cages 50
20 cm) was conducted in April 1994. In this experiment,
we were able to control prey intake and to determine the
relationship between prey mass and spider condition. Spiders
collected in the ﬁeld were assigned to one of three groups
after they built their ﬁrst web: in the ﬁrst group, spiders received three or four prey (houseﬂies) over 4 days, in the second group, they received one prey over the 4 days, and in the
third group they received no prey at all. The presence of a
web was noted each day, and after 4 days we weighed and
measured the spiders. We did not measure web size as this
was constrained by the size of the cage.
Cost of web building
The speed of radii construction was 20 times that of the speed
of constructing cribellate lines (mean SD, radii: 3.10 0.33
mm/s, cribellate lines: 0.15 0.02 mm/s, n 8). The length
of radii and of cribellate silk in a surface of 12 cm2 was highly
variable among spiders (length of radii: 279
28 mm, n
14 and cribellate silk length: 205 13 mm, n 14). For such
a surface, there was no correlation between spider body mass
and the length of the radii (r2
between mass and the length of the cribellate silk (r2
.60). The average time calculated to build a
complete surface of 12 cm2 was 1770 s (n
There was no signiﬁcant correlation between the time spent
to construct this surface and the mass of the spider (r2 .09,
.47). From the above calculations, the time necessary for building a web of 150 cm2, the average size of the
web found in the ﬁeld, is about 6 h.
The energetic cost of web building was assessed by measuring weight loss after web construction. We compared the residuals of a regression of the difference between the initial
and ﬁnal body mass against initial mass (log-transformed measurements) for spiders that had constructed a web overnight
and those that did not build a web. Individuals that built a
web lost signiﬁcantly more mass than those without a web (t
.002). Spiders that constructed a web
lost on average 8% (range: 1%–17%) of their body mass,
whereas those that did not build a capture web lost 5%
(range: 0%–9.5%). All of these spiders may have had some
exploratory and spinning activity while attaching their nests
to the fence. Spiders that had been acclimated to the fence
and already had functional webs lost on average 0.72%
( 5.5%–3.5%, n
20) of their body mass overnight. Thus,
on average, 3%–7% of body mass was lost during web-building
activity. The average web size constructed during this period
was 101 cm2 (SE
24), which is smaller than an
average-size web in the ﬁeld (150 cm2). Thus, the mass loss
calculated above is a conservative estimate of the cost of web
Frequency of web building in natural populations
Over the experimental period of 9 days, the median number
of days a functional web was present for the control spiders
was 6.5 in 1994 (range 2–9) and 7 in 1995 (range 3–9). The
median number of new webs per spider over this period was 118 Behavioral Ecology Vol. 10 No. 2 Figure 1
Mean body size (total length,
mm, 1 SD) of spiders at the
beginning and end of the ﬁeld
experiment in each of the
three groups in (a) 1994 and
(b) 1995. 1 in 1994 (0–2) and 0 in 1995 (0–3). These ﬁgures underestimate the frequency of web renewal because they do not take
into account partial web renewal. Web destruction or damage
occurred naturally due to prey-capture, wind, and livestock.
Using the spiders in the control group, we determined the
percentage of spiders in the population that had webs over
the period of the experiment. This varied from 50% (in wadi
2 in 1994) to 86% (in 1995) (see Figure 2). For each wadi,
there was no signiﬁcant difference among days in the percentage of spiders with webs (1994 wadi 1, G
2.91, df 7,
ns; wadi 2, G 2.98, df 7, ns; 1995, G 5.28, df 7, ns).
Neither was there signiﬁcant variation in the total number of
web-days in the three control groups (wadis 1 and 2 in 1994
and wadi 2 in 1995). Thus, any variation observed in the occurrence of new webs in the treatment groups could be attributed to the manipulations.
Inﬂuence of body size and condition on foraging decisions
Changes in spider size and condition
We determined the changes that occurred in spider size and
condition over the period of the ﬁeld experiment. The spiders were measured before the experiment began and at the end
of the experiment on day 9. Total body length (LGTH) and
body condition (residuals of LGTH on cephalothorax width,
CTW) were compared among the three treatment groups at
the end of the experiment. All size measurements were log
Final body length was analyzed by ANCOVA, with the initial
body length (measured before the start of the experiment) as
the covariate and the experimental treatment and year (1994
and 1995) as factors. The experimental treatment had an effect on ﬁnal body length (F2,106 2.913, p .059), and there
was no signiﬁcant difference between the years (F1,106 0.575,
p .45). However, there was a signiﬁcant interaction between
year and experimental treatment (F2,106
which indicates that the pattern of change in spider size differed in the 2 years (Figure 1). Indeed, in 1994, prey-supplemented spiders (fed group) increased in body size signiﬁcantly more than those whose webs were removed and not
given supplementary prey (web-removal group; Bonferroni
.013). In 1995, however,
adjusted pairwise comparison, p
the fed spiders were signiﬁcantly smaller in body size than the Pasquet et al. • Web building and foraging success in a desert spider 119 Table 1
Web-building responses of spiders in the ﬁeld experiment
Year 1, Wadi 1
Year 1, Wadi 2
Fed With webs (%) Total G (df 2) 3.135, ns
9.667 (p 100
25 13.257 (p
14.3 .01) 5
21 The percentage of spiders with new webs at the end of the
experiment is shown for each year and site separately. Figure 2
Percentage of spiders with webs over the duration of the ﬁeld
experiment in (a) 1994 (both sites combined) and (b) 1995 in each
of the three groups: control, web removal (web ) and
supplemented spiders (prey /web ). *The webs were removed on
days 0, 2, 4, and 6. control spiders at the end of the experiment (pairwise comparison, p .015), though not different from the web-removal group (p
.1). Initial body size did not differ among spiders assigned to the different treatments (ANOVA, F2,107
.31), but there was a weak effect of year (F1,107
Body condition (as indicated by the residuals of LGTH on
CTW) showed the same pattern as body length (above).
There was a signiﬁcant interaction between year and treatment group (ANOVA, F2,107 8.02, p .001), indicating that
the body condition of spiders in the three treatment groups
responded differently in the 2 years of the experiment. In
1994, only the fed group had a positive condition index (positive residuals), whereas in 1995, the condition index of the
fed group was negative. Thus, spiders that were supplemented
with prey in the ﬁrst year (1994) showed greater growth and
were in better condition at the end of the experiment than
spiders in the other treatment groups, while in the second
year (1995) feeding did not result in greater growth.
Inﬂuence on web building
In both years, the number of spiders with webs decreased with
time in the prey-supplemented group (Figure 2). In the con- trol and web-removal groups, the number of webs was variable, but with no general trend over the duration of the experiment.
At the end of the experiment, 22% of the fed spiders had
webs (data combined from the 2 years), in comparison with
69.4% of control spiders and 60% of the web-removal group.
Fewer fed spiders had webs in all three samples (year 1: wadis
1 and 2, year 2: wadi 2). The three treatments differed signiﬁcantly in two of the three samples (Table 1), and the combined probabilities of the three separate tests (Sokal and
Rohlf, 1981) show a signiﬁcant difference between the three
groups ( 2
The total number of days with a web (web-days) for preysupplemented spiders was less than for web-removed individuals that did not receive prey (mean
SD number of webdays, supplemented: 4.62
43, web removal: 6.26
2.12, n 34). The difference was signiﬁcant in the secondyear sample (ANOVA, F1,34 3.075, p .001), and combining
the probabilities of the three tests yielded a signiﬁcant difference overall ( 2
Inﬂuence on web size
To reduce the effect of daily variations in web size, we used
the average web area for each individual over the last 4 days
of the experiment as a measure of the spider’s response to
each treatment. The average web size was compared among
the three treatments. Web area measurements were log-transformed to normalize the data.
There was a signiﬁcant effect of the experimental treatments on web size (ANOVA, F2,79
.025), as well
as a signiﬁcant difference in web size between the years (ANOVA, F1,79 11.08, p .001), but no interaction between year
and treatment (p
.1). Webs of the fed spiders were signiﬁcantly smaller than those of the control spiders (Bonferroni
adjusted pairwise comparison, p .022), and this pattern was
consistent in both years (Figure 3).
We tested the web-building response in the laboratory on two
occasions, with 13 and 15 spiders, respectively. The results
were homogeneous, so we combined the data. Thus, 9 spiders
were fed 3–4 prey, 10 spiders were given 1 prey, and 10 were
given no prey over 4 days.
The results of the experiments in the laboratory conﬁrmed
those of the ﬁeld experiment (Table 2). Fewer new webs were
spun by well-fed spiders (three prey) than by spiders given Behavioral Ecology Vol. 10 No. 2 120 Table 2
Web-building responses of spiders under different feeding regimes
in the laboratory experiment
Percentage of spiders No prey 1 prey 3 prey With web (n
Without web (n
63.6 The percentage of spiders with new webs at the end of the
experiment (after removing all webs the previous day); 2
.05. Figure 3
Mean size of webs ( 1 SD) during days 4–8 of the ﬁeld experiment
(log-transformed web area, cm2) of spiders in each of the three
groups in 1994 (hatched bars, both sites combined) and 1995 (solid
bars). less food (one prey; Fisher’s Exact test, p
.070) or none at
all during the experiment (Fisher’s Exact test, p .015); there
was no difference between the latter two groups (Fisher’s Exact test, p
Our results show that spiders reduce their foraging effort following successful foraging. Spiders supplemented with food
decreased the size of the web, and many of them stopped
building altogether. The behavior of spiders whose webs were
removed but did not receive supplementary feeding did not
differ from the controls that were not prevented from foraging. Thus, the response of prey-supplemented spiders was not
due to web removal, but rather to the addition of prey.
All of the spiders increased in size and condition over the
course of the ﬁeld experiment, but there were differences in
the response to feeding in the 2 years of the experiment. In
1994, the fed spiders were signiﬁcantly larger and in better
condition than the web-removal and control spiders at the
end of the experiment, but this was not the case in 1995. The
different growth responses of spiders in the 2 years may be
related to the timing of the experiments. The second-year experiment was conducted early in the season, when spiders
were smaller (see Methods) and perhaps were constrained by
the amount of additional food they could consume. Although
fed spiders were in signiﬁcantly better condition only in one
year, in both years they reduced both web size and the frequency of web renewal. This suggests that the proximate cue
for web renewal is not body condition, but perhaps the presence or absence of prey. This idea is supported by other studies showing that insect activity (potential prey) can induce web
building and web relocation (Pasquet et al., 1994; Riechert,
In the ﬁeld experiment, spiders whose webs were removed
in the morning lost the opportunity to forage until the web
could be renewed in the evening. Repeated web removals
meant that these spiders could not forage during at least 4
days out of the 8-day experiment. This repeated disturbance
did not cause spiders to desert their web sites, unlike some
more mobile species (Leclerc, 1991). However, the loss of foraging time represented an extra cost for these spiders, and
we anticipated both greater loss of condition and increased
foraging effort than in the control or fed spiders (see Lubin
and Henschel, 1996). Nonetheless, web-removal spiders did
not differ in condition from the controls, nor did they differ in their tendency to renew the web. We conclude that food
supplementation over the relatively short period of the experiment could have a signiﬁcant effect on body condition
and behavior, but food deprivation over the same time period
had little effect. The lack of effect of food deprivation is perhaps no surprise, given that spiders are known to tolerate long
periods of fasting (reviewed by Nakamura, 1987).
We proposed that a time constraint on growth could increase the value of foraging relative to other activities. In the
case of S. lineatus, we predicted that the spiders would maintain an active capture web even when well fed. This prediction
was based on the assumptions that (1) S. lineatus has a short
growing season, (2) spiders that fail to mature in one season
will have low expected ﬁtness, (3) maintaining a web increases
the likelihood of capturing prey, and (4) increased prey capture translates into greater reproductive success (Schneider
and Lubin, 1977; Ward and Lubin, 1993). Our results were
contrary to the predicted outcome: the spiders reduced web
building when supplemented with prey. If we accept the basic
assumptions, one must then ask if we neglected to take into
account some aspect of the biology of S. lineatus, or if the
hypothesis itself is not supported here.
A reduction in foraging effort in well-fed individuals has
also been documented in other organisms (e.g., scorpions:
Skutelsky, 1996). This behavior can be attributed to satiation
or other digestive constraints or the existence of a large cost
to maintaining foraging activity, which decreases the marginal
beneﬁt of foraging. Proximate causes, such as satiation or digestive constraints, are inadequate explanations for the reduction of web building because a spider with a functional
web can capture prey and store it for later consumption. However, for S. lineatus, we showed that web construction carries
a large cost in terms of time (approximately 6 h to build a
complete web) and energy expenditure during web building
(as indicated by up to 10% loss of body mass per web). Web
construction in S. lineatus is time consuming because of the
slowness of laying down the sticky, cribellate threads (see also
Eberhard, 1988; Lubin, 1986). Aside from the direct energetic
cost, web-building activity exposes the spider to potential nocturnal predators. During the day, prey capture activity on the
web can be risky because of predators such as birds, lizards,
mantids, and wasps. These risks are similar for individuals in
any state, but spiders in good condition have less to gain from
renewing a web than individuals in poor condition.
There are also indirect risks associated with having a web:
it may attract predators to the nest. If an insect is trapped in
the web or captured and not consumed by the spider, it can
attract ants (Henschel, 1998; Schneider, 1995, 1996; Schneider and Lubin, 1997) as well as visually hunting predators.
The ants are not a direct threat to the spider (except when
moulting), but they often attack in large numbers, forcing the
spider to vacate its nest and sit exposed on the web or supporting threads. Our preliminary observations suggest that
ant attacks are frequent and that once ants discover a nest
with prey, this nest becomes a repeated target. Ants may be a Pasquet et al. • Web building and foraging success in a desert spider 121 threat particularly when several prey items are present in the
nest or web and when the prey insects are large and feeding
duration is long (personal observations; Schneider, personal
Our conclusion that S. lineatus modiﬁes web-building behavior in response to a short-term change in prey availability
agrees with other studies of web-building spiders that showed
an inﬂuence of previous foraging success on web-building decisions (Lubin and Henschel, 1996; Sherman, 1994). We had
proposed that a growth constraint over the spider’s lifetime
would change the beneﬁt-to-cost ratio of foraging in a risky
environment by increasing the value of continued foraging.
This was not the case, but whether physiological constraints
or direct and indirect risks of predation are responsible for
lower foraging effort following feeding remains to be investigated. Lubin Y, Kotzman M, Ellner S, 1991. Ontogenetic and seasonal changes in webs and websites of a desert spider. J Arachnol 19:40–48.
Lubin YD, 1973. Web structure and function: the non-adhesive orbweb of Cyrtophora moluccensis (Doleschall) (Araneae: Araneidae).
Form Funct 6:337–358.
Nakamura K, 1987. Hunger and starvation. In: Ecophysiology of spiders (Nentwig W, ed). Heidelberg: Springer-Verlag; 287–295.
Pasquet A, Ridwan A, Leborgne R, 1994. Presence of potential prey
affects web-building in an orb-weaving spider Zygiella x-notata.
Anim Behav 47:477–480.
Riechert SE, 1985. Decisions in multiple goal contexts: habitat selection of the spider Agelenopsis aperta (Gertsch). Z Tierpsychol 70:
Riechert SE, Luczak J, 1982. Spider foraging: behavioral responses to
prey. In: Spider communication: mechanisms and ecological significance (Witt PN, Rovner JS, eds). Princeton, New Jersey: Princeton
University Press; 353–385.
Schneider JM, 1995. Survival and growth in groups of a subsocial
spider (Stegodyphus lineatus). Insect Soc 42:237–248.
Schneider JM, 1996. Differential mortality and relative maternal investment in different life stages in Stegodyphus lineatus (Araneae,
Eresidae). J Arachnol 24:148–154.
Schneider JM, Lubin Y, 1997. Does high adult mortality explain semelparity in the spider Stegodyphus lineatus (Eresidae)? Oikos 79:
Sherman PM, 1994. The orb-web: an energetic and behavioural estimator of a spiders dynamic foraging and reproductive strategies.
Anim Behav 48:19–34.
Skutelsky O, 1996. Predation risk and state-dependent foraging in
scorpions: effects of moonlight on foraging in the scorpion Buthus
occitanus. Anim Behav 52:49–57.
Sokal RR, Rohlf FJ, 1981. Biometry. New York: W.H. Freeman.
Tanaka K, 1989. Energetic cost of web construction and its effect on
web relocation in the web-building spider Agelena limbata. Oecologia 81:459–464.
Uetz GW, 1992. Foraging strategies of spiders. Trends Ecol Evol 7:
Vollrath F, 1987. Growth, foraging and reproductive success. In: Ecophysiology of spiders (Nentwig W, ed). Heidelberg: Springer-Verlag;
Vollrath F, 1988. Spider growth as an indicator of habitat quality. Bull
Br Arachnol Soc 7:217–219.
Ward D, Lubin Y, 1992. Temporal and spatial segregation of webbuilding in a community of orb-weaving spiders. J Arachnol 20:73–
Ward D, Lubin Y, 1993. Habitat selection and the life history of a
desert spider Stegodyphus lineatus (Eresidae). J Anim Ecol 62:353–
Witt PN, Reed CF, Peakall DB, 1968. A spider’s web. New York: Springer-Verlag. We thank the Blaustein International Center for Visiting Scientist
Awards to R.L. and A.P. Research support was provided to A.P. by the
C.N.R.S. Gideon Kressel kindly helped obtain permission to use the
Bedouin grazing land for the project. We thank Samuel Venner for
help with the measurements of web building. The comments of J.
Henschel and an anonymous reviewer are gratefully acknowledged.
This is publication no. 256 of the Mitrani Center for Desert Ecology. REFERENCES
Eberhard WG, 1971. The ecology of the web of Uloborus diversus (Araneae: Uloboridae). Oecologia 6:328–342.
Eberhard WG, 1986. Effects of orb-web geometry on prey interception
and retention. In: Spiders: webs, behavior, and evolution (Shear
WS, ed). Stanford, California: Stanford University Press; 70–100.
Eberhard WG, 1988. Combing and sticky silk attachment behavior by
cribellate spiders and its taxonomic implications. J Arachnol 7:247–
Henschel JR, 1998. Predation on social and solitary individuals of the
spider Stegodyphus dumicola (Araneae: Eresidae). J Arachnol 26:61–
Henschel JR, Lubin Y, 1992. Environmental factors affecting the web
and activity of a psammophilous spider in the Namib desert. J Arid
Henschel JR, Ward D, Lubin Y, 1992. The importance of thermal
factors for nest-site selection, web construction and behaviour of
Stegodyphus lineatus (Araneae: Eresidae) in the Negev desert. J
Therm Biol 17:97–106.
Higgins LE, 1990. Variation in foraging investment during the intermolt and before egg laying in the spider Nephila clavipes. J Insect
Higgins LE, 1995. Direct evidence for trade-offs between foraging and
growth in a juvenile spider. J Arachnol 23:37–43.
Higgins LE, Buskirk RE, 1992. A trap-building predator exhibits different tactics for different aspects of foraging behaviour. Anim Behav 44:485–499.
Jakob EM, Marshall SD, Vetz GW, 1996. Estimating ﬁtness: a comparison of body condition indices. Oikos 77:61–67.
Krebs JR, Kacelnik A, 1991. Decision making. In: Behavioural ecology,
3rd ed. (Krebs JR, Davies NB, eds). Oxford: Blackwell Scientiﬁc;
Leborgne R, Pasquet A, 1987. Inﬂuence of aggregative behaviour on
space occupation in the spider Zygiella x-notata (Clerck). Behav
Ecol Sociobiol 20:203–208.
Leclerc J, 1991. Optimal foraging strategy of the sheet-web spider Lepthyphantes ﬂavipes under perturbation. Ecology 72:1267–1272.
Lima SL, Dill LM, 1990. Behavioural decisions made under the risk
of predation: a review and prospectus. Can J Zool 68:619–640.
Lubin Y, 1986. Web building and prey capture in the Uloboridae. In:
Spiders: webs, behavior, and evolution (Shear WS, ed). Stanford,
California: Stanford University Press; 132–171.
Lubin Y, Hennicke J, Schneider J, 1998. Settling decisions of dispersing Stegodyphus lineatus (Eresidae) young. Israel J Zool 44:217–226.
Lubin Y, Henschel J, 1996. The inﬂuence of food supply on foraging
behaviour in a desert spider. Oecologia 105:64–73. ...
View Full Document
- Spring '11