Adejeania vexatrix

The elongated, forward-projecting palpi are diagnostic and immediately separate this species from all similar western tachinids. Hystricia abrupta, an eastern species that resembles A. vexatrix in general coloration, lacks these elongated mouthparts entirely. Paradejeania rutilioides is more robust, spinier, and has more subdued orange coloration without the beak-like palps. Macromya crocata, found in similar forested habitats, also lacks the elongated palpi and is slightly smaller.

Large tachinid fly with bright orange abdomen contrasting against darker thorax. Abdomen covered with prominent, heavy black setae giving a bristly appearance. Most distinctive feature is the greatly elongated palpi that project straight forward from beneath the head, forming a sheath-like beak around the remaining mouthparts. Overall coloration slightly brighter than related species.

Open habitats in western North America including grasslands, sagebrush steppe, and montane meadows. Frequently associated with flowering rabbitbrush (Ericameria nauseosa) and other late-summer blooming plants in ponderosa pine woodlands and pinyon-juniper zones. Observed at elevations from approximately 4500 to 8300 feet.

Western North America from British Columbia and Alberta south through Wyoming, California, Arizona, New Mexico, and into Mexico. Core range spans the Intermountain West and southwestern United States.

Adults active July through August in northern portions of range; in southern areas (Arizona, New Mexico, southern California) activity extends into September and occasionally October. Peak abundance declines toward autumn.

• Lepidoptera (caterpillars) - parasitoidSpecific host species undocumented; known to parasitize caterpillars but identity of prey species remains unrecorded

Tachinid life cycle: females deposit eggs or larvae on or near host caterpillars; larvae penetrate host and develop internally, eventually killing the host; pupation occurs in soil or host remains; adults emerge to feed on nectar and mate. Specific timing and developmental details for this species unrecorded.

Adults are regular flower visitors, observed taking nectar from late summer and fall wildflowers particularly Ericameria nauseosa (rubber rabbitbrush). When approached, individuals frequently fly before allowing close observation or photography. Nocturnal activity unknown.

Biological control agent; parasitoid of caterpillars that helps regulate lepidopteran populations. Adult flower visitation contributes to pollination services, complementing bees and other pollinators in late-season flowering communities.

Beneficial insect providing ecosystem services through caterpillar population suppression and pollination. No known negative impacts. Occasionally encountered by entomologists and naturalists during late-season collecting in western North America.

• Paradejeania rutilioidesLarger, more robust body with more subdued orange coloration; more heavily spined; lacks elongated palpi; active later in season (August–December)
• Hystricia abruptaEastern North American species with similar orange-and-black coloration but lacks elongated palpi entirely; allopatric distribution
• Macromya crocataSimilar forested habitat use and general appearance but smaller, lacks elongated palpi

• Tachinidae
• parasitoid
• western North America
• flower visitor
• diagnostic morphology

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Two Spiny-butts
• Oecanthidae | Beetles In The Bush