Laboratory evaluation of aggregation, direct mutual interference, and functional response characteristics of Pseudacteon tricuspis Borgmeier (Diptera: Phoridae)

Studies of parasitoid behavior yield information on behavioral strategies, and are crucial tests of theoretical models. The studies reported here provided insights into behavioral and functional responses of the red imported fire ant (Solenopsis invicta Buren) parasitoid, Pseudacteon tricuspis (Borgmeier) that were previously unknown. Laboratory studies were performed to quantify aggregative responses of P. tricuspis adults to variable host ant densities, determine effect of direct mutual interference between multiple ovipositing P. tricuspis females confined with host S. invicta, elucidate the effect of confining one or two additional males with premated females on progeny sex ratios, and determine the form of the functional response of individual ovipositing P. tricuspis. Consistent with theory and field observations, P. tricuspis tended to aggregate at host patches containing greater numbers of ants. Some evidence of direct mutual interference was found, as per capita oviposition success declined when more than one female was confined and weak, but significant, reductions in searching efficiency were found when more than two P. tricuspis females are simultaneously ovipositing. The presence of one or two males did not appear to affect ovipositional efficiency of solitary premated females, but normally male–biased sex ratios of progeny trended toward a 1:1 ratio when the number of males was increased from zero to two. None of the linear parameters in the logistic models were significantly different from zero suggesting that P. tricuspis had constant, type 1, attack rates regardless of host density, at least under our laboratory experimental design.