Yellow Swarming Fly vs Caribou Bot Fly

Side-by-side species comparison

Attribute Yellow Swarming Fly Caribou Bot Fly
Scientific Name Thaumatomyia notata Cephenemyia jellisoni
Order Diptera Diptera
Family Chloropidae Oestridae
Size 2-2.5 mm 12-16 mm
Habitat Grasslands Heathland
Diet Predators Omnivores
Regions Europe Alaska, northern Canada, Yukon, Northwest Territories
Conservation Least Concern Least Concern

Yellow Swarming Fly

A tiny yellow fly famous for forming enormous hibernation aggregations in buildings, sometimes numbering millions. Larvae are predatory on root aphids in grassland.

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Did You Know?

Can form hibernation clusters of millions in attic spaces, with individual aggregations weighing several kilograms.

Caribou Bot Fly

A robust, furry fly that parasitizes caribou and deer in North America. Like its Eurasian relative, it deposits larvae near the nostrils of its host. Adults have vestigial mouthparts and survive entirely on stored energy.

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Did You Know?

Infected caribou may sneeze violently to expel mature bot fly larvae from their nasal passages before the larvae pupate in the soil.