Cremastocheilus canaliculatus

Distinguished from other Cremastocheilus species by the presence of a distinct longitudinal groove (canaliculatus = "channeled") on the pronotum or elytra. Most similar to other eastern Cremastocheilus species, but specific identification requires examination of pronotal and elytral sculpturing patterns. The combination of small size, flattened form, dull black coloration, and association with ant mounds separates this genus from other eastern scarab beetles. Adults may be found in ant nests or crash-landing near foraging trails during dispersal flights.

Associated with ant colonies, particularly mound-building species in the genus Formica. Occurs in diverse terrestrial habitats including forests, prairies, and open woodlands where host ants are present. The beetles inhabit the interior of ant nests and the surrounding soil periphery.

Eastern North America: Canada (Ontario, Quebec); United States (Connecticut, Georgia, Indiana, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Vermont).

Adults disperse in spring to locate new host colonies. New adults emerge from pupal cells in late summer or early fall, then enter ant nests to overwinter. Active feeding on ant brood resumes in spring.

Adults are specialized predators of ant larvae and pupae. Larvae feed on decaying organic matter, likely the composted vegetation accumulated by host ants within nest mounds.

• Formica - primary hostmound-building thatching ants
• Myrmecocystus - hosthoneypot ants
• Lasius - hostcornfield ants
• Camponotus - hostcarpenter ants
• Pogonomyrmex - hostharvester ants
• Veromessor - hostharvester ants
• Aphaenogaster - hostspine-waisted ants

Females lay eggs singly in soil around ant nest periphery. Larvae pass through three instars, feeding on decaying nest material and defended by striking mandibles and repulsive secretions. Pupation occurs in oval chambers constructed from soil particles. Development from egg to adult requires approximately four months. Adults accumulate colony scent while moving slowly toward nest center, becoming chemically integrated with host ants.

Adults employ thanatosis (death-feigning) to gain entry to ant nests, remaining motionless with legs outstretched in areas trafficked by foraging workers. Ants retrieve the seemingly inert beetles as food items. Adults possess modified mouthparts: an enlarged shield-like mentum covers other mouthparts from below, while maxillae are adapted into piercing structures for penetrating ant larvae and pupae. Mandibles are reduced and function only in transporting liquid food.

Predator within ant colonies, exerting top-down pressure on host brood populations. The relationship represents a specialized form of social parasitism. Population densities of 20-200 beetles per nest have been recorded, suggesting potentially significant impact on individual host colony dynamics.

No direct economic importance. Occasionally encountered by entomologists and naturalists excavating ant nests. The species contributes to scientific understanding of myrmecophily and chemical integration between insects.

• Other Cremastocheilus speciesMorphologically similar; require examination of pronotal grooves and elytral sculpturing for definitive identification. C. canaliculatus distinguished by the eponymous channel/groove.
• Valgus canaliculatusShares specific epithet and family, but belongs to tribe Valgini with scale-like setae and termite associations rather than ant associations. V. canaliculatus males visit flowers; Cremastocheilus adults do not.

• myrmecophile
• social parasite
• predator
• thanatosis
• Scarabaeidae
• Cetoniinae

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Bug Eric: Anteater Scarab Beetles
• Spring beetles on Coreopsis flowers | Beetles In The Bush
• Ants invade Beetles in the Bush! | Beetles In The Bush