Only adult fleas bite. The adult flea is elongated, 1-3 mm long and has flat sides. They look like small grasshoppers. The flea’s ability to jump is well known. An adult flea can jumps vertically up to 20 cm. Fleas are dark-colored.
The head, the thorax which consists of three segments and abdomen are all covered in backward-facing hairs, thorns and outgrowths, all facing backwards so the flea can only move forward when crawling in feathers or hairs. The tube-like mouth parts are located on the lower part of the head. It is thin and can be pierced into the skin. Although the adult fleas are easy to see, it is not possible to determine the species without using a microscope.