The diets of Rhinolophus rouxi and Hipposideros lankadiva were studied during October 1984 in Sri Lanka, by analysing the faeces collected from individuals. As a comparison, insects were collected with a light trap at different sites in the study area.
Rhinolophus rouxi showed no specialization for any particular insect prey. The diet composition in this species shows a good correspondence to the composition in dry weight of insects collected by light traps. Dipterans were under-represented in the faeces compared to the numbers trapped. This suggests that R. rouxi forages unselectively on prey larger than the generally very small dipterans. After the first monsoon showers, the remains of beetles, especially scarabaeids, and termites were more common in the faeces of R. rouxi. Bats caught at hourly intervals during one night showed an increase in the proportion of moths consumed.
In contrast, H. lankadiva was found to feed mainly on beetles, particularly scarabaeids, together with large, slow-flying insects such as bugs or nuptial ants. The proportion of beetles (79%-100%) in the faeces of this species was about three times higher than their representation in the insect collections. This suggests that H. lankudiuu forages selectively.