A Comparative Functional Approach to the Host Detection Behaviour of Parasitic Wasps. 2. A Quantitative Study on Eight Eucoilid Species

This paper reports on a comparative study of the host detection behaviour of 8 parasitoid species belonging to three eucoilid genera. They attack larvae of Drosophilidae in different microhabitats. We measured behavioural variables such as time allocation to components like 'probing the substrate', 'walking' and 'standing still', frequency and duration of and variation in 'probes' and 'walks', searching efficiency and behavioural reaction to host movement. Variation in several variables is largely congruent with the systematic classification of the species in the three genera, and is correlated with the role different stimuli play in actual host location. There is a significant positive correlation between the percentage of time spent standing still and the percentage of hosts found through the sensing of host movement. Species that locate their hosts mainly by sensing host movement (Ganapsis spp.) spend most of their time standing still and use their ovipositor in a different way than species that mainly locate their hosts by regularly probing the substrate (Leptopilina spp.). Kleidotoma spp. use a combination of these two stimuli and so show a combined, more complex behaviour. Differences were also found between species of one genus and between strains of one species. Although in general the type of substrate females normally search on or the kind of host species that they attack does not seem to have influenced the searching behaviour, some small differences between species could be considered adaptations to different environmental conditions. Different species that attack the same host species in the same microhabitat show great differences in host detection behaviour. For these parasitoid species this may provide a means by which they can coexist.