Bombylius mexicanus

Adults can be distinguished from the related genus Systoechus by the location of the r-m vein on the wing. Members of the genus Bombylius tend to be active in spring, while Systoechus species are more active in fall. The species is part of the tribe Bombyliini within the subfamily Bombyliinae.

Hairy, bee-like fly with a single pair of wings (characteristic of Diptera). Possesses an exceptionally long proboscis adapted for reaching deep into flowers to sip nectar. The body is covered in dense setae that trap pollen, aiding in incidental pollination. Wing venation includes the r-m vein, which is used to distinguish it from similar genera such as Systoechus.

Found in sand prairie remnants and open sandy areas. One documented observation occurred in the Mississippi lowlands of southeastern Missouri on sandy ground.

Widespread in North America: from Ontario and British Columbia in Canada, south through the United States, and into Mexico.

Active as adults in spring. A fresh-looking individual was observed in mid-May in southeastern Missouri.

Adults feed on nectar from flowers using their long proboscis. They do not deliberately collect pollen as food.

• solitary bees - parasitoidBee flies in the genus Bombylius are known to parasitize the larvae of solitary bees. Females follow bees back to their nests and deposit eggs in or near the burrow. The fly larva enters the bee gallery, consumes the provisions left by the bee, then attaches to and feeds on the developing bee larva.

Complete metamorphosis with egg, larva, pupa, and adult stages. Eggs are deposited in or near solitary bee nests. Larvae are parasitoids that develop within bee nests, first consuming food provisions then feeding on the host bee larva. The larval stage lasts approximately 12–15 days based on observations of related species.

Adults are hyperactive, skittish, and difficult to approach. They exhibit rapid flight and are frequently observed hovering near flowers. When disturbed, they attempt immediate escape flight. One observed individual was documented falling onto its back after striking a plant during escape, then righting itself and flying away.

Adults serve as incidental pollinators due to their hairy bodies trapping and transferring pollen between flowers. Larvae function as parasitoids of solitary bees, regulating bee populations. The species occupies a position as both mutualist (pollination) and antagonist (parasitism) within its ecosystem.

Contributes to pollination of wildflowers. May be encountered by naturalists and photographers due to its bee-mimic appearance. Not known to be a pest or directly beneficial to agriculture.

• Systoechus spp.Similar appearance and both in tribe Bombyliini, but distinguished by r-m vein position on wing and fall activity period versus spring activity in Bombylius.
• Anthrax spp.Related bee flies in family Bombyliidae, but parasitize different hosts including tiger beetle larvae rather than solitary bees.

• bee fly
• parasitoid
• pollinator
• bee mimic
• spring active
• North America

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Field Guide Selected References
• One-Shot Wednesday: Upside down bee fly | Beetles In The Bush
• Bombyliidae | Beetles In The Bush | Page 2
• Diptera | Beetles In The Bush | Page 5
• May | 2012 | Beetles In The Bush
• Beware the bee fly - Bombylius sp. — Bug of the Week