if hes alone it can hardly be a sibling, but im thinking cricket or some of those small annoying fruit flie sized flies that arent fruit flies, i have lost some snails and a tarantula to those, they went in and laid eggs in the T's burrow then while it was molting their spikes / maggots started munching away on the T, same deal with the snails, so now i have secured all my slings/juvies and remaining 2 snails with pantihose as an extra layer on the vent screening.