Changing oviposition times of the crab spider Misumena vatia (Thomisidae) correlate with climate change

Abstract

The crab spider Misumena vatia (Clerck, 1757) (Thomisidae) is an important sit-and-wait predator at flowers visited by nectar or pollen-seeking insects. Typically, female M. vatia molt into their adult stage when many insect-attracting flowers come into bloom, and the spiders quickly gain weight leading up to oviposition. Between 1979 and 2010, the first spider ovipositions shifted one month earlier, from late July to late June, at my study site in coastal Maine, USA, in accordance with a concurrent temperature increase of ca. 0.44°C and a lengthening growing season. Flowering times of the spiders' most important hunting site, common milkweed Asclepias syriaca, as well as recruitment dates of their most important prey, bumblebees Bombus spp., to flowering milkweed, advanced as well. The shift in spider oviposition times increased the feasibility of second broods, though I found no successful second broods in the field, and the success of such broods would be problematic because of heavy overwintering losses. Differing rates of change of spider, milkweed and bumblebee activity indicated decreasing synchrony among these species; in particular, lessening future hunting opportunities for the spiders.