Infection with a parasitic mite does not affect the number of prey consumed by the two-spotted lady beetle

Background/Question/Methods The two-spotted lady beetle, Adalia bipunctata, is susceptible to a parasitic mite, Coccipolipus hippodamiae. In European populations of A. bipunctata, infection by C. hippodamiae causes pathogenic effects including poorer overwintering survival in males and lower female fecundity. We hypothesized that infected A. bipunctata suffer from additional pathological effects such as a reduction in their ability to capture prey such as aphids. To test our hypothesis, we established colonies of A. bipunctata and C. hippodamiae from individuals collected on the campus of Gonzaga University in Spokane, Washington, USA. We conducted laboratory experiments on consumption of aphid prey by infected and uninfected A. bipunctata. We measured the number of aphids consumed by A. bipunctata over 48 hours. We conducted our experiments in two different venues: small plastic containers and individual fava bean plants.

Results/Conclusions In the plastic containers, A. bipunctata females consumed significantly more aphids than did males (86% versus 52% of aphids offered were consumed by females and males, respectively). However, we did not find a significant difference in the number of aphids consumed by infected versus uninfected A. bipunctata (65% versus 74% of aphids offered were consumed by uninfected and infected beetles, respectively). Similarly, on fava bean plants, infection status did not affect aphid consumption by female A. bipunctata. Behavioral observations found that infected and uninfected A. bipunctata had similar time budgets in the plastic containers. Further experiments will address whether the infection status of A. bipunctata changes their nutritional requirements.