Stegodyphus sarasinorum, , Karsh, 1891

Drisya-Mohan, Ovatt Mohanan, Kavyamol, Pallath & Sudhikumar, Ambalaparambil Vasu, 2019, Effect of Kleptoparasitic Ants on the Foraging Behavior of a Social Spider (Karsch, 1891)., Zoological Studies 58 (3), pp. 1-11 : 5-6

Kleptoparasites of Stegodyphus sarasinorum

Before starting the experiments common kleptoparasites of S. sarasinorum were observed and collected from the field. Four species of spiders and two species of ants were collected. Collected species include spiders Argyrodes kumadai Chida and Tanikawa 1999 (Male and female), Oxyopes javanus Thorell 1887 , Phintella vittata Koch 1846 , Hyllus semicupreus Simon 1885 and ants Oecophylla smaragdina Fabricius 1775 and Anoplolepis gracilipes Smith F 1857 . A. kumadai was collected from the web and others were found inside the nest of S. sarasinorum ( Fig. 3 ).

Effect of exposure of ants on web building behavior

From previous studies, it is known that web building is influenced by the previous feeding. This led to the curiosity for examining the influence of ants on the web building capacity. As long as the web remains intact, spiders do not prefer to expand their web. To induce web rebuilding, it may, therefore, be necessary to destroy the webs. So we removed the old web completely from the K unexposed and K exposed fasted and fed groups. The experimental groups of both fed and fasted spiders rebuilt the web from the first day onwards. The rebuilding of the web is a foraging decision. In the first day of K unexposed spider groups, web rebuilding differed in fed (129.05 ± 19.82 cm 2) groups than the fasted group (314 ± 9.86 cm 2, t (2.93) = 8.353, p = 0.003, Table 1). Hence, after ant exposure, the web rebuilding was comparatively less in the fed spider (96.5 ± 6.87 cm 2) than the fasted spider group (120.13 ± 15.14 cm 2, Table 1), though no significant difference was found (t (2.28) = 1.516, p = 0.253, Table 1).

The size of the web of both K unexposed fed and fasted spider groups were compared during 4 successive days ( Fig. 4 ). There was a statistical difference in mean web size in K unexposed, between fed and fasted spider groups as determined by two-way ANOVA (F (1,16) = 252.4, p = 3.22 e- 11) but there was no statistically significant interaction between the fed and fasted spiders on the 4 experimental days (F (3,16) = 2.664, p = 0.0831). And also in the case of K exposed fed and fasted groups, significant difference in the size of the web was observed (F (1,16) = 15.858, p = 0.001) but the interaction between the day and K status was not significant(F (3,16) = 0.605, p = 0.621, Fig. 5 ).

Considering the fed spiders, there was no significant difference in the means of the web sizes of K unexposed and K exposed spiders (F (1,16) = 1.419, p = 0.251) on any of the experimental days (F (3,16) = 2.119, p = 0.138), whereas the means of the web sizes of K unexposed and K exposed fasted spiders differed significantly (F (1,16) = 316.2, p = 5.81 e- 12) ( Fig. 6 ) but there is no interaction between the “day” and “K-status” effects (F (3,16) = 2.83, p = 0.071).

Effect of exposure of ants on prey capturing behavior

We observed the influence of ants on prey capture, handling time and prey ingestion. It was found that the first reaction to the prey didn’t differ in the two cases considered, i.e., K exposed and K unexposed spider groups, both approximately 5 minutes (W = 9, p = 0.87). All throughout the four experimental days, it was observed that the vibration in the web was the cue that attracted the spider toward its prey and not the presence or absence of kleptoparasites. The three species of prey and their respective weights did not affect the pattern of prey capture in any way, i.e., there was no difference in the frequency of successful prey capture between K exposed and K unexposed groups, 12 cases considered (W = 12, p = 0.18). When the spider approached the prey, they tightened the silk with the tarsi of the front leg. A single individual always attacked the prey first, but this was often quickly followed by other spiders. The first capture part of the prey item was different; it may be leg, antennae, abdomen or head. The Spearman’s rank correlation suggested a positive correlation between the handling time of the K exposed groups and three times of the day (R s = 0.608, p = 0.03). However, the K unexposed groups didn’t show any significant correlation with the times of the day (p = 0.071). The results of the Wilcoxon rank sum test showed that the mean ranks of the handling time in the two groups, i.e., K unexposed and K exposed groups didn’t differ significantly (W = 64, p = 0.663). Even though the K exposed group was found to be positively correlated with the different times of the day, the overall prey handling time needed for the spiders to immobilize the prey was similar in the two cases considered ( Fig. 7 ). Results of the Two-way ANOVA indicated that there was no significant difference in the mean difference in prey injection activity between the 2 groups (F (1,18) = 0.07, p = 0.79). This is independent of “all the three times of the day” (F (2,18) = 1.25, p = 0.30).

(A)

(C)

(E)

Figures

Fig. 3. Kleptoparasites of S. sarasinorum. (A) Argyrodes kumadai (Dewdrop spider). (B) Hyllus semicupreus (Heavy-bodied jumper). (C) Phintella vittata (Banded phintella). (D) Oxyopes javanus (Lynx spider). (E) Oecophylla smaragdina (Weaver ant). (F) Anoplolepis gracilipes (Yellow crazy ant). Photo courtesy of: Karunnappilli S. Nafin.

Fig. 4. Web rebuilding ability (Size of the web (cm2 ± SEM) of the K unexposed (Kleptoparasite “K” is O. smaragdina) spider groups (Fasted (n = 3 groups) and Fed (n = 3 groups)) during the 4 experimental days. The regression lines, blue line (Fasted spider) has the Intercept a = 236.94, Slope b = 71.812 and Coefficient of Determination R² = 0.966 and the red line (Fed spider) has a = 78.925, b = 55.61 and R² = 0.955.

Fig. 5. Web rebuilding ability (Size of the web (cm2 ± SEM)) of the K exposed (Kleptoparasite “K” is O. smaragdina) spider groups (Fasted (n = 3 groups) and Fed (n = 3 groups)) during the 4 experimental days. The regression lines, blue line (Fasted spider) has the Intercept a = 64.13, Slope b = 73.361 and Coefficient of Determination R2 = 0.96 and the red line (Fed spider) has a = 41.5, b = 65.25 and R2 = 0.948.

Fig. 6. Size of the web (cm2 ± SEM) built by fed and fasted (K unexposed (“- K exposure”): n = 3 groups) and K exposed (“+ K exposure”): n = 3 groups) spider groups.

Fig. 7. Handling time (minutes) of both K unexposed (Ku, n = 3 groups) and K exposed (Ke, n = 3 groups) spider groups recorded during three different times (9 am, 1 pm and 5 pm) of the four experimental days.