Efficiency of vibrational sounding in the parasitoid Pimpla turionellae isaffected by female size

The pupal parasitoid Pimpla (=Coccygomimus) turionellae L. (Hymenoptera: Ic hneumonidae) attacks a broad range of lepidopteran pupae. The variation in host size translates into substantial differences in size among adult paras itoids. Pimpla turionellae shows a strong host size-dependent sex allocatio n, which indicates that parasitoid body size influences sex-specific effect s on fitness costs. We tested whether the body size of females affects thei r capacity to locate hosts by vibrational sounding. We investigated parasit oids from three size categories with respect to their ability to find artif icial hosts (cigarette filters) in cylinders made of thin or thick paper (2 0 or 65 g/m(2), respectively). Using laser Doppler vibrometry, we measured vibration signals produced by large and medium-sized females during vibrati onal sounding. Large females produced vibrations of a higher intensity than , but a similar frequency to, their smaller conspecifics. The parasitoid's ability to locate a hidden host model by vibrational sounding also improved with size. This indicates that parasitoid size is an important factor in d etermining the female's host-searching success. We discuss the results in r elation to the parasitoid's behavioural ecology. (C) 2001 The Association f or the Study of Animal Behaviour.