Pollenia is a common and widespread genus of flies known as cluster flies. There are at least 102 Pollenia species worldwide, 6 species in North America north of Mexico, and 4 species in Minnesota. It occurs worldwide mostly in the Northern Hemisphere, and to a lesser extent in the Southern Hemisphere. It is common throughout North America and Europe.

The biology of Pollenia is poorly known. Many species are parasitic on earthworms. The female lays her eggs on soil known to be inhabited by earthworms. When the eggs hatch, the larvae burrow into the soil in search of a host. A few species are known to parasitize caterpillars and bees.

Photo by Alfredo Colon

Pollenia are often extremely common in urban and agricultural areas. They can be the most abundant species visiting flowers in gardens. When the weather cools, they seek shelter from the cold, often in the walls and attics of humans’ homes. On warm winter days and in early spring they become active. They are often seen clustered at windows seeking escape. This is the source for the common name of the genus. If a large fly appears in your house in midwinter, it is probably a cluster fly.

Description

The following description refers only to the species that occur in North America.

Pollenia are small to medium-sized flies. They are similar in appearance to house flies but slightly larger. The body is dull, not metallic.

The thorax is covered with crinkly, golden-yellow hairs (setae), but these may wear away as the fly ages. On most species there are no pale longitudinal stripes on the thorax. Pollenia vagabunda has a single stripe in the middle (middorsal), but this is sometimes indistinct.

The abdomen is hairy and dark gray with black and pale patches.


Distribution
		Sources 24, 27, 29, 30, 82, 83.
9/6/2024


Taxonomy
Order	Diptera (flies)
Suborder	Brachycera
Infraorder	Cyclorrhapha
Zoosection	Schizophora
Zoosubsection	Calyptratae (calyptrate flies)
Superfamily	Oestroidea (bot flies, blow flies, and allies)
Family	Polleniidae

Subordinate Taxa
Until recently, it was thought that the genus Pollenia was represented by a single species, Pollenia rudis, in North America. Following recent revisions of the genus (Rognes, 1991; and Whitworth, 2006) there are now six species recognized in North America.
black-bellied cluster fly (Pollenia amentaria) common cluster fly (Pollenia rudis) cluster fly (Pollenia griseotomentosa) cluster fly (Pollenia labiais [=Pollenia intermedia]) narrow-cheeked cluster fly (Pollenia angustigena) tufted cluster fly (Pollenia pediculata) vagabond cluster fly (Pollenia vagabunda)

Synonyms


Common Names
cluster flies

Glossary

Seta

A stiff, hair-like process on the outer surface of an organism. In Lepidoptera: A usually rigid bristle- or hair-like outgrowth used to sense touch. In mosses: The stalk supporting a spore-bearing capsule and supplying it with nutrients. Plural: setae. Adjective: setose.


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Alfredo Colon


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CLUSTER FLY Pollenia
Rob Curtis

About

Nov 19, 2017

Pollenia GRAY CLUSTER FLY. Willow Springs, IL. 11/1/2016.

Cluster Flies (Calliphoridae: Pollenia) Mating
Carl Barrentine

About

Aug 7, 2011

Photographed in Wisconsin, across the Mississippi River just North of Red Wing, Minnesota (04 August 2011). Thank you to 'v belov' (@Bugguide.net) for identying the genus for these specimens!

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