Pollenia griseotomentosa

Jacentkovský, 1944

cluster fly

Pollenia griseotomentosa is a Palaearctic cluster fly and the smallest British in the Pollenia, measuring 4.5–8.0 mm in body length. It is distinguished from by specific morphological characters including lack of pale wing tuft, yellow to pale brown thoracic lappets, dark palpi and basicosta, and characteristic bristle patterns. Like other cluster flies, overwinter in sheltered locations including buildings, where they aggregate in large numbers and may become nuisance pests. The species has been introduced to North America, with records from Canada and the northeastern United States.

Pronunciation

How to pronounce Pollenia griseotomentosa: //ˌpɒˈliːniə ˌɡraɪˌziːoʊˌtoʊmənˈtoʊsə//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other Pollenia by combination of: lack of pale wing tuft; yellow to pale brown (not dark) thoracic lappets; dark palpi and basicosta; and specific patterns of thoracic and abdominal bristles. Accurate identification typically requires examination of setae number, position, and length on various body parts. Separated from the common Pollenia rudis and P. pediculata by these subtle morphological characters not generally visible in field images of living specimens.

Appearance

Small cluster fly, 4.5–8.0 mm body length, the smallest British Pollenia . with golden-gray tomentum; lacks pale wing tuft present in some . thoracic lappets yellow to pale brown. Palpi and basicosta dark. Bristle patterns on thorax and provide key diagnostic characters for species identification within the .

Habitat

seek sheltered locations for , including buildings, wall voids, and window frames. Collection records indicate presence in marshes (Marston Marsh, Norwich) and woodlands (Wytham Woods, Oxfordshire). Spring and summer adults found on flowers.

Distribution

Native to the Palaearctic region: Andorra, Austria, Belarus, Belgium, Czech Republic, Denmark, Finland, France, Germany, Great Britain, Hungary, Italy (mainland and Sardinia), Latvia, Netherlands, Poland, Russia, Slovakia, Spain, Sweden, Switzerland, Turkey, Ukraine. Introduced to Nearctic Region: Canada (British Columbia, Ontario) and USA (New York, Western Virginia).

Seasonality

period in Britain: March to October. active in spring and summer, feeding on flowers; overwinter as adults in sheltered locations. Unseasonable warm temperatures in mid-winter may cause adults to become active and move indoors.

Diet

feed on nectar from flowers. Larval diet unknown; other Pollenia are of earthworms.

Life Cycle

. and larva remain undescribed for this . has been described. Overwinters as in sheltered locations. For the generally, larvae are of earthworms: eggs laid in soil, larvae enter worms and feed internally for approximately two weeks before exiting to pupate in soil; pupal stage lasts 39–45 days; up to four per year.

Behavior

exhibit aggregating , clustering in large numbers in sheltered sites including buildings—hence the "cluster flies." Adults may become active on warm winter days and attempt to escape to the outdoors, often accumulating at windows. Do not bite humans or pets. When disturbed or crushed, may produce faint odor but less pronounced than some related blow flies.

Ecological Role

serve as when visiting flowers. Potential mechanical of due to habit of entering buildings and contact with human environments, though not known to transmit specific . Larval role in unknown, but related may regulate earthworm .

Human Relevance

Considered a nuisance pest due to in buildings. enter through small openings in window frames, wall voids, and other gaps, sometimes accumulating by the hundreds in older homes. Do not bite, sting, or carry known . Smashing individuals may leave greasy stains. No effective economic control measures; prevention through sealing building entry points is recommended. sequenced as part of Darwin Tree of Life Project.

Similar Taxa

Pollenia rudisMost common cluster fly in North America; larger size; differs in thoracic lappet coloration and bristle patterns
Pollenia pediculataCommon cluster fly; similar habit of in buildings; distinguished by subtle differences in setae patterns and body proportions
Pollenia vagabundaRecent European introduction to North America (1950s); similar nuisance ; requires microscopic examination for reliable separation
Muscina pascuorumAlso enters buildings in autumn and winter; distinguished by different (Muscidae), lack of golden thoracic tomentum, and association with fungi rather than earthworms

More Details

Genome resources

High-quality assembly generated as part of the Darwin Tree of Life Project: 1,046.30 Mb total assembly size, 6 chromosomal pseudomolecules (5 + X ), complete mitochondrial genome of 17.23 kb. Genome available through Wellcome Open Research and associated databases.

Taxonomic history

Described by Jacentkovský in 1944. Until recently, many cluster flies were misidentified as Pollenia rudis; modern recognizes six in North America and multiple species in Europe, differentiated by fine morphological characters.