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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. Key words: Coleoptera, ecology, behaviour, moonmilk, cave hygropetric. Primerjava jamskih higropetričnih hroščev in njihovegaprehranjevanja; Cansiliella servadeii in Hadesia asamo (Coleoptera, Leiodidae, Cholevinae, Leptodirini) Številni hrošči iz poddružine Leptodirinae (Leiodidae) so prilagojeni na življenje v posebnem habitatu »jamskem higropetriku «, t.j. tankem sloju tekoče vode, ki teče po sigi. Zaenkrat je njihovo vedenje še precejšnja neznanka. Visoko specializirani higropetrični vrsti Cansiliella servadeii in Hadesia asamo sta geografsko ločeni in filogenetsko nesorodni. Ker je prva očitno vezana na depozite mehke sige (t.i. jamsko mleko), smo želeli raziskati iskanje hrane pri tej vrsti ter primerjati strategijo hranjenja obeh vrst. Da bi povečali zanesljivost rezultatov, smo poleg in situ opazovanja C. servadeii iz jame Grotta della Foos (Italija) in H. asamo iz jame Bravenik (Bosna in Hercegovina), njuno vedenje tudi posneli. Z vrstičnim elektronskim mikroskopom smo raziskali obustne okončine in stopalca obeh vrst in jih primerjali s H. weiratheri iz Črne gore, da bi preverili potencialne morfološke prilagoditve na specifično ekološko nišo. Bistvene razlike v zgradbi ustnega aparata so najverjetneje posledica razlik v strategiji hranjenja, kot tudi različne splošne ekologije omenjenih vrst. V prispevku predstavljamo, primerjamo in razpravljamo o novih opažanjih povezanih z gibanjem in prehranjevanjem higropetričnih hroščev. Ključne besede: Coleoptera, ekologija, vedenje, jamsko mleko, jamski higropetrik.

The microbial diversity of moonmilk, a hydrated calcium carbonate speleothem, was evaluated from two Italian caves to provide context for the food web of highly-specialized troglobitic beetles, Cansiliella spp. (Leptodirinae), with distinctive carbon and nitrogen isotope values indicative of a novel food source. The moonmilk and associated percolating waters had low to no extractable chlorophyll, with an average organic C:N ratio of 9, indicating limited allochthonous input and a significant contribution from microbial biomass. The biomass from moonmilk was estimated to be ~104 micro- and meiofaunal individuals per m2 and ~107 microbial cells/ml. Proteobacteria dominated the 16S rRNA gene sequences retrieved from the moonmilk from both caves. The distribution of other proteobacterial classes and phyla in the moonmilk were statistically similar to each other, even though the two caves are geographically separated from each other. Comparing the moonmilk gene sequences to sequences from previously described environmental clones or cultured strains revealed the uniqueness of the moonmilk habitat, as ~15% of all of the moonmilk sequences were more closely related to each other than to sequences retrieved from any other habitat. However, comparative analyses confirmed that as much as ~34% of the clones sequences were also closely related to environmental clones and cultured strains derived from soil and freshwater habitats, which is likely due to the fact that the putative inoculation source for the moonmilk bacterial communities is from overlying soil and percolating fluids from the surface. Prior to our studies of Cansiliella spp., moonmilk has not been considered a food source for cave animals. Our findings provide unique insight into moonmilk microbial diversity that could reveal the underpinnings of the moonmilk carbon and nitrogen cycle that influences the isotopic composition and the morphological adaptations of the troglobitic beetles associated with the moonmilk.