Deer Fly

Deer Fly
  • Size: About 6 to 10 mm long
  • Color: Black with blue or green reflections
  • Distinctive Feature: Clear edges on wings, aggressive behavior
  • Habitat: Wooded areas, near animals


The deer fly, scientifically known as Lipoptena cervi, is distinguished by its unique physical characteristics. As an adult, it measures about 4 to 5 mm long, with a brownish or grayish body. Its wings, although functional, are often lost after the insect has found a host, leaving a more rounded body. Its legs are sturdy and equipped with claws, allowing it to cling firmly to its host. The eyes of the deer fly are large and prominent, and it has short antennae.


This species is typically found in forests and wooded areas of Quebec. It prefers moist and shady environments conducive to the survival of its hosts, mainly deer. These flies are not active flying insects; they spend most of their life cycle on or near their host. The larvae develop in the forest environment, often in the soil or leaf litter, where they molt several times before reaching adulthood.


The behavior of the deer fly is closely related to its parasitic life cycle. Adults are hematophagous, feeding on the blood of their hosts, mainly deer, but sometimes also other mammals, including humans. Their activity is more pronounced in late summer and autumn, during which they actively seek a host for feeding and reproduction. Once attached to a host, the deer fly can remain on it for several days, even weeks, feeding regularly on blood. This behavior makes it a potential vector of diseases for animals and, in rare cases, for humans.

Distinguishing Deer Flies from Other Insects

House Fly

House Fly

The deer fly is distinctly different from the house fly in size and behavior. While the house fly measures about 6 to 7 mm, the deer fly is generally smaller, measuring 4 to 5 mm. In terms of behavior, the house fly is often observed moving quickly and flying around homes and waste, whereas the deer fly prefers to stay on or near its host to feed on blood. The house fly also has a more balanced body and more visible wings compared to the deer fly, whose wings often become rudimentary.

Manure Fly

Manure Fly

The manure fly, often found near decomposing organic materials, is distinguished from the deer fly by its golden or metallic green color. It is also slightly larger and has a more active flying behavior. The manure fly is more likely to be found on farms or near compost piles, while the deer fly is specifically adapted to forest life and a blood-feeding regime on mammals.

Black Wasp

Black Wasp

Black wasps are significantly larger than deer flies, with a size that can reach up to 30 mm. They also have distinctive features such as two pairs of wings and a narrowed waist between the thorax and abdomen, typical of wasps. Moreover, unlike the deer fly, black wasps are predators or scavengers and do not feed on blood.



The hornet, much larger than the deer fly, can measure up to 55 mm. It is distinguished by its robust body, large wings, and striped abdomen. The hornet is a social insect living in colonies, unlike the deer fly, which leads a more solitary existence. Hornets are also known for their painful sting, a trait absent in the deer fly, which is a blood-sucking parasite.

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