Gone with the wind: wind-induced web movement reduces kleptoparasite abundance in a golden orbweaver spider

Obligate kleptoparasitic spiders (Argyrodinae, Theridiidae) live as thieves in the webs of larger hosts. Web size has long stood above all other variables in predicting how many kleptoparasites occupy a given web, best documented in the large orb webs of golden orb-weavers (Nephilidae). Yet no study has asked whether wind-a ubiquitous force acting on every aerial web-also influences kleptoparasite abundance. Prompted by the observation that exposed, wind-buffeted webs of Trichonephila inaurata in the spiny forest of Ifaty, southwestern Madagascar, appeared to carry fewer kleptoparasites than sheltered webs of similar size, we conducted a rapid, intensive survey of 60 webs along two transects in a single afternoon. We quantified wind effect as the maximum lateral sway of the web hub over one minute, controlling for web area. We found a strong negative effect of wind-induced web movement on kleptoparasite number; trumping the positive effect of web size. Wind effect thus emerges as a previously unrecognized axis structuring the distribution of spider kleptoparasites.