Meloe angusticollis

Distinguished from congeners by moderate to dense punctation on the head and pronotum, combined with a conically produced scutellum. Elytra are extremely short, not reaching the end of the abdomen, giving a 'waistcoat' appearance. Body color is black or metallic blue with sparse, short setae matching the integument. Outer metathoracic tibial spur has the apical portion produced anteriorly. Females average 9–19 mm; males are smaller.

Found in open habitats including grasslands, meadows, and areas with wildflower-rich vegetation. Associated with habitats supporting solitary bees, which serve as hosts for larvae.

Northern half of the United States and southern Canada. Records include Alberta, British Columbia, and Manitoba in Canada.

Active primarily during spring and early summer. Adults emerge in spring, with peak activity from March through June depending on latitude.

Adults feed on leafy vegetation including Astragalus and other herbaceous plants. Larvae are parasitoids of solitary bees, consuming nest provisions and host eggs.

• Solitary bees (Apidae, various genera) - parasitoidTriungulin larvae hitchhike on bees to reach nests
• Astragalus lentiginosus - food plantAdult food source at some localities

Complete metamorphosis with hypermetamorphosis. Eggs laid in soil, often near or within bee burrows. First-instar larvae (triungulins) are mobile with well-developed legs; later instars become sedentary and engorged. Triungulins climb vegetation to await bees, attach to visiting females, and are transported to nests where they feed on provisions and host eggs. Overwinters as late-stage larva, pupates in spring. Typically one generation per year.

Adults release oily droplets of hemolymph from leg joints and body when disturbed, containing cantharidin. Females excavate soil to access bee burrows for egg-laying, sometimes enlarging existing burrow entrances. Triungulin larvae exhibit cooperative aggregation behavior to enhance bee attraction.

Parasitoid of solitary bees; population dynamics linked to bee host availability. Chemical defense compounds may be sequestered or utilized by predators such as nuthatches, which have been observed rubbing blister beetles on tree cavities, presumably to repel competitors or predators.

Cantharidin causes blistering on contact with skin; potentially fatal if ingested (approximately 100 mg lethal dose). Historical use as 'Spanish fly' aphrodisiac, now discontinued due to toxicity. Agricultural concern when beetles are inadvertently baled in hay and fed to livestock, causing lethal poisoning.

• Meloe franciscanusSympatric in western North America; distinguished by different host bee associations and subtle morphological differences in punctation and scutellum shape
• Other Meloe speciesM. angusticollis specifically identified by conical scutellum and head/pronotum punctation pattern; most congeners have different scutellum morphology or punctation density

• blister beetle
• oil beetle
• hypermetamorphosis
• bee parasite
• cantharidin
• chemical defense
• Meloidae
• North America
• solitary bee parasitoid
• triungulin

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Meloidae Holdings | Entomology Research Museum
• The Amazing Bee-Parasite Research of Leslie Saul-Gershenz | Bug Squad
• Ground nesting bees beware of blister beetles - Meloe spp. — Bug of the Week
• Blistering beetles - Meloe spp. — Bug of the Week
• Springing into action – oil beetles and citizen science! - Buglife Blog - Buglife