Sentence:  Another group of insects that tend to be very secretive in their habits and were very well represented in the ancient forest are the <WSD>bark lice</WSD>, or psocids.68 <WSD>Bark lice</WSD> (90) are usually solitary, but sometimes the adults and nymphs live together under webs spun out of silk emitted from head glands. They are found not only in litter but, as their name implies, on and under bark. 
Meaning of the word marked with <WSD> tags:  Any insect of the order Psocoptera, that live on or near trees and feed on algae and lichen.