Axymyiidae

Genus Guides

A small of nematoceran flies comprising four extant and nine described , with eight additional fossil species. is the sole member of the infraorder Axymyiomorpha, though historically classified within Bibionomorpha. The family is distributed across the Holarctic and Oriental regions. Larvae are xylophilic and semi-aquatic, developing in saturated decaying wood.

Protaxymyia thuja by Jacqui Simmons. Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Axymyiidae: //æksɪˈmɪɪəˌdiː//

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Identification

Distinguished from Bibionidae by four branches of the radial (Bibionidae have two or three). Separated from other nematoceran by the combination of: short 14-16 segmented ; ocelli on a prominence; reduced mouthparts; and specific wing venation pattern including radial vein 4 branched to crossvein. Male structure with condition and size dimorphism is distinctive.

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Habitat

Larvae inhabit saturated, decaying wood in stream environments and very wet, often submerged logs of various tree . collected in forested including Vaccinium myrtillus-type pine- and spruce-dominated forests. Semi-aquatic conditions required for larval development.

Distribution

Holarctic and Oriental regions. Eastern Nearctic: twenty U.S. states and two Canadian provinces. Palearctic: including Russian Karelia (Paanajarvi National Park). Historical phylogeographic expansion from southern Appalachian refugium northward following last glacial maximum, with possible northern refugia in Driftless area and southeastern Ohio.

Seasonality

emerge synchronously in spring. Collection records indicate activity in late spring (June).

Life Cycle

, larva, pupa, and stages documented. Larvae develop in saturated decaying wood in semi-aquatic conditions. combines terrestrial adult phase with aquatic/semiaquatic larval development in wood substrates.

Behavior

Synchronous spring of . Extremely rare in collections; adults captured using .

Similar Taxa

BibionidaeSimilar general appearance, but distinguished by radial branching (two or three branches versus four in ) and other wing venation details.

More Details

Taxonomic history

Often included within infraorder Bibionomorpha in older classifications; now recognized as sole member of Axymyiomorpha. Molecular phylogenetic analysis recovers as monophyletic with closest relatives in Culicomorpha.

Rarity and discovery

Extremely rare in entomological collections. New continue to be described; Plesioaxymyia imprevista described from Russian Karelia in 2024 represents sister to all other species in molecular .