Wikipedia
Eucinetidae
Eucinetidae is a family of beetles, notable for their large coxal plates that cover much of the first ventrite of the abdomen, sometimes called plate-thigh beetles. The family is small for beetles, with about 37 species in nine genera, but are found worldwide.
Adults are generally elliptical in shape, ranging from 0.8 to 4.0 mm in length, and black or brown in color. The head is small and bent underneath.
Eucinetids live in detritus or in fungus-covered tree bark, where both adults and larvae eat various sorts of fungi.