The Greater Bamboo Lemur, Prolemur simus, can be found in the Talatakely region of Ranomafana National Park in Madagascar. The lemur feeds almost exclusively on Cathariostachys madagascariensis, a large bamboo species. During feeding, the Greater Bamboo Lemurs splits open bamboo culms to access the inner pith. Once opened, these culms attract a species of fly which can be observed actively feeding on the opened bamboo. This study examined the possibility of an interaction between the fly, the lemur, and the bamboo. Flies were counted at lemur-opened bamboo and manually-opened bamboo found at various distances from active feeding sites. It was found that significantly more flies were present on those bamboo culms which were opened by the lemurs than those which were manually opened. As Prolemur simus was classified as critically endangered by the IUCN Red List in 2006, the fly may also be endangered. This is an example of why there is a growing need to understand the interactions of insects with other organisms as a route to establishing the status of insect populations, which are otherwise difficult to accurately monitor.