Using controlled exposure trials to assess predation and parasitism of the Kamehameha butterfly (Nymphalidae: Vanessa tameamea)

The Kamehameha butterfly (Nymphalidae: Vanessa tameamea) is Hawaii’s official state insect and is one of only two native butterflies. Unfortunately, the once common butterfly is rarely seen today, and has been extirpated from many areas. The reason behind its decline is uncertain, but it is likely due to impacts by non-native insects, parasitoids, and birds, in addition to host plant declines.  To quantify impacts of predators and parasitoids, we established laboratory colonies of the butterfly and deployed eggs and caterpillars under three different exclusion treatments: birds excluded, birds and ants excluded, and completely exposed.  After three days, parasitism and predation was assessed.  To date, over 850 caterpillars and 400 eggs have been deployed across four sites.  Predation and parasitism varied by site, but overall we found that birds accounted for 7-21% larval disappearance, and ants accounted for up to 10% disappearance over only a three day period. In contrast, parasitism of deployed larvae has been extremely low (less than 1%).  For egg deployments, we found there to be a 37% predation rate, likely due to introduced katydids. Egg parasitism varied by site; whereas three of our sites have had no egg parasitism, one site has had over 80% of eggs parasitized. At the end of this study, we hope to gain insight into the decline of V. tameamea, and initiate efforts to repopulate this species and prevent further decline of this iconic insect.