cluster fly

American  

noun

1. a black fly, Pollenia rudis, slightly larger than the housefly, commonly found hibernating in large numbers in homes in the fall.

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cluster fly British  

noun

1. a dipterous fly, Pollenia rudis, that tends to gather in large numbers in attics in the autumn: family Calliphoridae. The larvae are parasitic in earthworms

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Example Sentences

“But just as often it’s, like, a flesh fly, a bottle fly or a cluster fly, and those are really great and interesting species that you should know about.”

From New York Times

The common occurrence in such places of the cluster fly and a few other species, which may be easily mistaken for the house fly, is responsible for the prevailing belief as to the way the house fly overwinters.

From Project Gutenberg

It gets its name of "cluster fly" from its habit of collecting in compact groups or clusters in protected corners during cold periods.

From Project Gutenberg