BITING PEST is a term used to describe small insects that bite humans and animals. The three crossword solutions for this term are GNAT (4 letters), FLEA (4 letters), and REDANT (6 letters). A GNAT is a small, two-winged fly that can bite humans and animals. Fleas are small, wingless insects that feed on the blood of humans and animals. Redants are small, reddish-brown ants that bite humans and animals. All three of these insects are considered biting pests.