THE TIME AND EGG BUDGET OF LEPTOPILINA-CLAVIPES, A PARASITOID OF LARVAL DROSOPHILA

1. For the understanding of the influence of natural selection on the persistence of host selection behaviour in populations of Drosophila p arasitoids it is important to know whether parasitoids will become tim e- or egg-limited. We investigated whether the Drosophila parasitoid L eptopilina clavipes (Hartig) meets egg- or time-limited conditions in the field. 2. To this end the following aspects of the parasitoid's li fe were studied: egg load at emergence, travelling velocity between pa tches, patch residence times, oviposition rates and life expectancy. T ogether with the results from earlier studies on host and patch distri butions, this formed the input of a 'Monte Carlo' simulation model, in which the life history of an individual parasitoid can be traced. 3. The simulations revealed that under the conditions found in the field 12.9% of the parasitoid population is egg-limited. The model was also run for a number of scenarios which reflect 'good' or 'bad' circumstan ces. In most cases a significant proportion of the parasitoid populati on proved to be egg-limited. 4. For the measurement of travelling velo cities and patch residence times a marking method, especially applicab le to small-sized parasitoids such as L. clavipes, is described. Marki ng did not affect survival, host habitat location or host detection ra te. Parasitoids were found to be attracted to the odour of fruit-bodie s of Phallus impudicus, the most important breeding substrate of their hosts.