Cave hygropetric beetles and their feeding behaviour, a comparative study of Cansiliella servadeii and Hadesia asamo (Coleoptera, Leiodidae, Cholevinae, Leptodirini).

Several Leptodirini beetles (Leiodidae) are known to dwell in hygropetric habitats where films of water run down the cave walls, but observations of their behaviour are lacking. The ultra- specialised hygropetricolous beetles belonging to the genera Cansiliella and Hadesia are biogeographically and phylogenetically unrelated leptodirines. As the species of the former genus are known to be associated with the moonmilk deposits our study aimed to obtain data on their foraging behaviour, as well as to compare the feeding strategies of both genera. In situ monitoring of C. servadeii from the cave Grotta della Foos (Italy) and H. asamo from Bravenik Cave (Bosnia and Herzegovina), was complemented by video recordings to ensure accurate results. Mouthparts and tarsi of both species were examined using scanning electron microscopy and compared with H. weiratheri from Montenegro to evaluate potential morphological adaptations to the hygropetricolous ecological niches. The three species had significantly different mouthpart morphologies, likely due to differences in semi-aquatic feeding strategies and overall ecology. A series of new observations on site movement and feeding behaviour are presented, compared and discussed.