Ask The Entomologist

Louse flies

It’s autumn. Among the many little signs of this are the appearance of Western Deer Keds, or louse flies, as they’re often called. As I was walking in the woods this past week, a number of them flew about me, a couple landed on my hand and ran up and down my arms. A poor life choice for them, as they were swiftly collected.

Louse flies are members of family Hippoboscidae, and are best known for their very odd reproduction. They have their young one at a time, much like us humans. Females fertilize a single egg from stored sperm, the egg then hatches inside the mother fly’s reproductive tract. The resulting maggot nurses from a “milk” gland and molts several times inside the uterus. After about a week of this, the mother fly gives birth to a large late-stage maggot. In the case of the Western Deer Ked, the mother generally does this where the deer beds down for the night.

Liptoptena depressa, a deer ked, courtesy of my in-laws’ dog (an unsuitable host).

The late-stage maggot pupates immediately. After emerging from its pupal case as an adult in the fall, the new adult louse fly will take off in search of a suitable host. Once it finds a host, it will start feeding on blood, shed its wings, and will remain on the host until its dying day. Western Deer Keds can survive on Mule Deer, White Tailed Deer, Elk, and Moose. They may try to feed on other species – they can certainly bite. But they won’t be able to survive for long off of their proper hosts.

Keds are best known as livestock pests – sheep keds are somewhat famous for the economic damages they can inflict. Native to Europe, sheep keds immigrated with humans, and are present across almost all of North America and much of South America, as well as parts of Africa, Asia, and Australia. While sheep keds have been reported, there is not good evidence that they can survive long on Bighorn Sheep or Mountain Goats.

If you hunt turkey, and have tried for the “Grand Slam” you might have encountered turkey keds in the American southeast as well. There’s several species of turkey keds, but to the best of my knowledge, none have made it west of the Rocky Mountains yet.

Have you met louse flies before? When, and on what?

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