Résumé
Parasites are expected to be associated with host developmental instability because developmentally unstable hosts may be more susceptible to, or more frequently exposed to, parasitic infections compared with developmentally- stable ones, or because parasites may directly disrupt host development. In this study, we analysed the relationship between developmental stability in the weta Pleioplectron simplex (Orthoptera) and infections by hairworm and mermithid parasites. These parasites have a long development in their host and the size of adult worms exceeds the length of the host by a considerable amount (15-20 cm). For one character (femora) we found that fluctuating asymmetry was significantly higher in parasitized individuals compared with unparasitized ones, in each of two samples collected in different years. Because no relationship was observed between the level of fluctuating asymmetry and the parasite size or number, however, infection by hairworm and mermithid parasites could be more a consequence of developmental instability than a cause. For other characters (tibia, external and internal spines of femora), the level of fluctuating asymmetry between parasitized and unparasitized individuals was not significantly different. Our results are discussed in relation to ecological constraints met by hairworm and mermithid parasites to complete their life cycle.