CONTRASTING PATCH CHOOSING BY ANTHOPHILOUS AMBUSH PREDATORS - VEGETATION AND FLORAL CUES FOR DECISIONS BY A CRAB SPIDER (MISUMENA-VATIA) AND MALES AND FEMALES OF AN AMBUSH BUG (PHYMATA-AMERICANA)

Field-collected individuals of Misumena vatia and Phymata americana we re compared experimentally as to the kind of vegetation and flower cue s they use to choose a hunting site, by introducing them into choice a renas with variously manipulated natural stems of three species of pla nt and with artificial flowers. Misumena vatia showed a strong prefere nce for stems with flowers or leaves or both; P. americana did not pre fer normal stems as strongly and it did not show a statistically signi ficant preference among the various manipulated patches. Both predator s discriminated among Solidago canadensis, Daucus car ota, and Cirsium arvense, showing a clear preference for the first. Misumena vatia sho wed a clear preference for yellow artificial flowers on wooden sticks when given a choice of four different colours. Phymata americana prefe rred yellow or blue to white or red, showing no discrimination between colours of the same group (yellow vs. blue or white vs. red). Misumen a vatia took the longest time (ca. 43 min) to complete its choice of s tem; female and male P. americana took Is and 15 min, respectively. In all the experiments P. americana showed sexual diethism, the females being more choosy than the males. The ranking of discrimination from g reatest to least was as follows: M. vatia, females of P. americana, an d males of P. americana. We suggest that both species of predators hav e different strategies of patch choice and that in the case of P. amer icana, males and females have different patterns of patch selection, t he males searching not only for prey but also for mates.