Blera flukei

Distinguished from other Blera species by the combination of: elongate conical face with pronounced antennifers creating deeply excavated profile; orange antennae with pale brown arista; scutum with narrow anterior yellowish pile fascia (absent in some males); female with wholly brassy yellow scutal pile; second tergite with large triangular brassy yellow pile patch on sides; small yellow pile patch on anterior angles of fourth tergite; tibiae with black bands. The deeply excavated facial profile behind antennae is particularly distinctive.

Medium-sized hoverfly, 11–13 mm. Head: face elongate conical, pale yellow pollinose with short black and yellow hair; gena with small brown spot near oral margin; vertical triangle shining black with long black hair; ocellar triangle and upper occiput black; frontal orbits pale yellow pollinose; antennifers pronounced, creating deeply excavated facial profile; antennae orange with pale brown arista; occiput gray pollinose with brassy yellow hair (upper orbital cilia black). Thorax: scutum shining blue-black with black pile, often with narrow anterior yellowish pile fascia; female scutum pile wholly brassy yellow; gray pollen patch inside humeri. Abdomen: shining blue-black with mostly black pile; sides of second tergite with large triangle of brassy yellow pile; small patch on anterior angles of fourth tergite; external genitalia may be partly or wholly pale pilose. Wings: ashy gray, hyaline; anterior veins reddish yellow; wing base pale orange; vein R4+5 almost straight, joining costa just before wing tip; first posterior cell (r4+5) acute apically, extending nearly to wing margin. Legs: black and yellow; femora black with black pile, reddish yellow distally; tibiae yellow with black bands covering median third or more; tarsi yellow except distal two tarsomeres black.

Associated with mature woodlands containing trees with rot holes or sap-exuding wounds. Larval habitat specifically in decaying heartwood cavities and sap flows of living or dead trees.

Nearctic: northern United States and southern Canada. Recorded from Alaska to Oregon, Idaho, and across the northern tier of contiguous United States.

Adults feed on nectar and pollen from flowers. Larvae feed on exuding sap or in rot holes of trees.

Larvae are rat-tailed type, adapted to aquatic or semi-aquatic conditions in tree cavities. Development occurs in exuding sap or rot holes of trees. Adults emerge and visit flowers. Specific pupation site and overwintering stage not documented.

Adults hover in flight and visit flowers. Hovering behavior allows nearly motionless station-keeping in air.

Adults contribute to pollination through flower visitation. Larvae participate in decomposition processes in tree rot holes and sap flows, contributing to nutrient cycling in woodland ecosystems.

Rare species of conservation interest. No documented economic importance or pest status. Subject of biological recording and conservation monitoring due to rarity and association with old-growth woodland habitats.

• Blera fallaxAnother Blera species with similar woodland association and rat-tailed larvae; distinguished by facial and abdominal pile patterns, and by distribution (B. fallax is Palearctic, B. flukei is Nearctic)
• Other Blera speciesShare genus-level traits of rat-tailed larvae in tree rot holes; require examination of facial excavation depth, antennal color, and specific abdominal pile pattern for separation

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Conservation Translocations: It’s Not Just Beavers - Buglife Blog - Buglife