Polypedilum Kieffer, 1912

Namayandeh, Armin, Hudson, Patrick L., Bogan, Daniel L. & Hudson, John P., 2024, Chironomidae (Diptera: Insecta) of Alaska, USA, with descriptions of new species and a checklist, Zootaxa 5511 (1), pp. 1-95 : 82-83

Polypedilum Kieffer, 1912

Polypedilum species have been separated into subgenera based on adult morphology only ( Saether et al. 2010). The larval characters are unavailable to sustain this division ( Epler et al. 2013). Four of these subgenera occur in Alaska: Pentapedilum , Polypedilum , Tripodura , and Uresipedilum .

Bowser et al. (2020) identified Polypedilum (Pentapedilum) tritum (Walker, 1856) based on DNA barcodes of larval specimens collected in the Slikok Creek Watershed in Kenai National Wildlife Refuge. We collected P. tritum adults from around an unnamed lake in Kanuti National Wildlife Refuge in late July and a larva from Troublesome Creek in the Mat-Su Valley. We have also collected another larva that resembles P. tritum from the South Fork of Little Campbell Creek near Anchorage. This larva has a longer blade than P. tritum , and the ratio of ventromental plates length to the distance between the ventromental plates is 2.3.

Six species in the subgenus Polypedilum are known from Alaska. We collected a Polypedilum (s.s.) castornama Maschwitz, 2000 adult male from Auke Lake in mid-August. Bowser et al. (2020) collected Polypedilum (s.s.) cultellatum Goetghebuer, 1931 from the Slikok and Miller Creek watershed. Maschwitz & Cook (2000) described Polypedilum (s.s.) prolixipartum and Polypedilum (s.s.) tuberculum from Alaska based on the specimens obtained by Sommerman & Simmet (1965) ’s car-top trap along the Seward and Glenn Highways (Highway 1) from Girdwood to Palmer. We collected larvae in the Polypedilum (s.s.) illinoense group from Swan Lake near Ketchikan, the Usuktuk River near Atqasuk in the Arctic Coastal Plain, and from Little Meadow Creek in the Mat-Su Valley. We collected larvae of the Polypedilum (s.s.) fallax group from a tributary to Georges Inlet on Revillagigedo Island. We also collected unknown larval specimens from a Yukon River delta distributary.

We collected adult males and pupae of Polypedilum (Tripodura) pullum (Zetterstedt, 1838) from the Yukon River delta in late June, which is the first faunistic record for the USA. We collected Polypedilum (Tripodura) scalaenum (Shrank, 1803) adult males and pupae from Yukon River. This is a new faunistic record for Alaska. We collected larvae of Polypedilum (Tripodura) scalaenum group in Spike Creek on Revillagigedo Island, from the Usuktuk River in the Arctic Coastal Plain and Little Meadow Creek in the Mat-Su Valley. We collected Polypedilum (Tripodura) simulans Townes, 1945 adults from around an unnamed lake in Kanuti National Wildlife Refuge in late July, and adults and pupae from the Yukon River delta distributary in mid-July. These are new faunistic records for Alaska.

The only species in the subgenus Uresipedilum in Alaska is Polypedilum (Uresipedilum) pedatum Townes, 1945 reported by Thompson & Epler (2009) from Attu Island and our collection of a male from the Margaret Bay area on Revillagigedo Island in late April.

Other records of Polypedilum include larvae from Southeast Alaska and reports from Toolik Lake by Hershey (1985), from Lone Spruce Pond by Kaufman et al. (2012), and from streams in the Arctic Coastal Plain in Arctos (2023). Epler et al. (2013) previously noted that larvae of Polypedilum occur in virtually all still and flowing waters, with the exception of waters in the Arctic and high mountains. The finding of larvae in Arctic Alaska adds to the extent of the distribution of this genus. The larvae of Polypedilum primarily inhabit soft sediments of flowing waters, but can also be found on hard substrate, mining in water plants, and colonizing plant-held waters like those found in pitcher plants ( Epler et al. 2013).