Parasitism by the mite <i>Trombidium breei</i> on four U.K. butterfly species

Abstract 1. The incidence of parasitism by larvae of the mite species Trombidium breei was reported in one population of the lycaenid butterfly Polyommatus icarus , four populations of the satyrine butterfly Maniola jurtina , one population of the satyrine butterfly Aphantopus hyperanthus , and two populations of the satyrine butterfly Pyronia tithonus , as well as on one specimen of the dipteran Alophorus hemiptera . A considerable proportion of butterflies (11‐50%) was infested in all study populations. 2. The pattern of infestation was examined in detail in M. jurtina . Males had a significantly higher incidence of infestation than females, and middle‐aged butterflies had a higher incidence of infestation than old or young butterflies. The incidence of infestation peaked in the middle of the flight season, and this seasonal effect was independent of the effect of butterfly age. 3. Using a model based on capture‐recapture data, it was estimated that a hypothetical ideal male M. jurtina that lives exactly the mean expected lifespan of 9‐10 days has an approximately 75% chance of becoming infested with mites at least once during its lifetime, a mean time to first infestation of 3‐4 days, and an average infestation persistence time of 2‐3 days. 4. Capture‐recapture data failed to show any effect of mite infestation on the lifespan or within‐habitat movement rate of M. jurtina . 5. In experiments in which individual butterflies were taken out of their normal habitat and released, M. jurtina and P. tithonus that were infested with mite larvae did not differ from uninfested individuals in the efficiency with which they returned to suitable habitat. Thus, parasitism by T. breei larvae had no detectable effects on flight performance or orientation ability. 6. The results suggest that trombidiid mite larvae have limited potential in the biological control of insect pests.