Ornithonyssus sylviarum

Darkened feathers due to a heavy infestation in the vent area of a laying hen. 
The entire life cycle of the northern fowl mite is completed on the bird. The mites are irritating to people and sometimes cause dermatitis in egg handlers and farm workers.
zenz54.jpg (4413 bytes) Sternal shield. 
The female typically has only two pairs of setae on the sternal shield; the third pair is on the unsclerotized integument.