Psilopsocus mimulus
Psilopsocus mimulus is a bark louse from Australia and the first member of its order known to bore into wood. It belongs to the family Psilopsocidae, with the life cycle going from egg to nymph to adult.
Nymphs are very different from adults because they live in wood. The earliest nymphs are almost colorless, except for the last two body segments which are brown, hardened, and covered with long hair-like structures. They have eight-segment antennae. Later nymphs look quite different: the head is almost as wide as the abdomen, their antennae have a curved first segment, and they show wing buds. The abdomen’s rear third is heavily hardened and black, looking almost cylindrical from above, and the end is densely bristly. This unusual end has a look that reminds some beetles.
Adults are 4.0–4.5 mm long, with eyes, antennae longer than the body, and full wings. They can live from about 6 to 67 days in the lab, usually under 40 days. Female adults begin laying eggs about 4 days after the last nymph molt. Eggs are laid one at a time on bark and are camouflaged with crusty brown fecal material. The egg stage lasts about 20–26 days, then the cycle starts again.
P. mimulus was known since 1963, but its wood-boring habit was discovered in 1993. Nymphs live in tunnels up to 6 cm long in pine twigs. They plug the tunnel entrance with their hardened abdomens (a behavior called phragmosis) and bore their own tunnels rather than reuse old ones. They produce brown fecal pellets, sometimes with digested fungi and woody material. Nymphs may leave tunnels briefly to feed on bark fungi, but this is rare. After molting, a nymph may stay in its tunnel or move to another.
An unknown chalcidoid wasp parasitizes P. mimulus nymphs inside their tunnels. A white fungus has been seen on dead nymphs, but its role is unclear. The latridiid beetle Corticaria japonica also lives in empty tunnels from mid‑November to January, and several beetles can share a tunnel.
This page was last edited on 3 February 2026, at 00:16 (CET).