This image depicts a dorsal view of a female deer fly, Chrysops dimmock, which had been collected at Nickerson State Park, Cape Cod, MA, on July 4, 2013. This particular specimen had been feeding on both human beings and canines who’d been walking upon a trail near a pond. There are many different species of deer flies in the genus Chrysops, in North America. Most are small and yellow, and inflict a painful bite.

Deer fly larvae breed in moist habitats, such as in mud along the edge of streams or ponds. Adults emerge during the summer, and females begin to bite humans, horses, dogs, deer and other mammals in their search for blood. Males do not bite, and are found on flowers where they collect pollen.

Females use their sharp mouth parts like a scissors to stick, and cut through the skin or hide of their hosts. This creates sharp pain and a pool of blood. The fly then injects saliva into the wound and sponges up the blood before it coagulates.

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