Cremastocheilus quadratus

Fall, 1912

anteater scarab beetle

Cremastocheilus quadratus is a myrmecophilous scarab beetle in the Scarabaeidae, first described by Fall in 1912. Like other members of its , it lives within colonies as a of ant larvae and pupae. The is found in the southwestern United States and northwestern Mexico.

Pronunciation

How to pronounce Cremastocheilus quadratus: /krɛmæsˈtoʊkiːləs kwɒˈdreɪtəs/

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Identification

of Cremastocheilus quadratus share the diagnostic features of the : small size (approximately 10 mm), flattened and angular body form, dull black coloration with dense, heavily armored bearing pits or wrinkles. The are normally concealed in grooves beneath the . Specific identification to level requires examination of detailed morphological characters; the species epithet 'quadratus' suggests a quadrate or squared body shape relative to .

Habitat

Associated with nest mounds, particularly those of mound-building ant . In the desert southwest where the reaches greatest diversity, found in areas with thatching ant (Formica) colonies and other ant species.

Distribution

Southwestern United States (Arizona, California) and northwestern Mexico (Baja California).

Seasonality

disperse to find new colonies in spring. New adults emerge from pupal in late summer or early fall. Activity within nests occurs year-round, with on ant concentrated in spring when host colonies are active.

Diet

feed on larvae and pupae. Larvae feed on decaying vegetation that ants have composted within nest mounds.

Host Associations

Life Cycle

Females lay singly in soil around nest periphery. Larvae pass through three instars, feeding on decaying vegetation in ant mounds, and can defend themselves against ants with mandibular strikes and repulsive secretions. occurs in oval chambers constructed from soil particles. Complete cycle from egg to takes approximately four months.

Behavior

enter nests by 'playing dead' () in areas trafficked by ants, using a convincing death-feigning posture with legs outstretched. Ants, being scavengers, carry the beetles into nests. Newly emerged adults slowly move to nest centers, accumulating colony scent to avoid detection. Adults are capable of fast, sustained but crash-land in areas frequented by scouting ants.

Ecological Role

within colonies, regulating ant numbers. The relationship is parasitic rather than mutualistic.

Human Relevance

Occasionally encountered by entomologists and naturalists excavating colonies. Not of economic importance.

Similar Taxa

  • Other Cremastocheilus speciesApproximately 35 North American share the myrmecophilous lifestyle and general ; specific identification requires detailed examination. C. quadratus distinguished by quadrate body shape implied by species name.
  • Other myrmecophilous beetles (e.g., certain Staphylinidae)Also live in colonies but belong to different with distinct body plans; staphylinids are more elongate with short , while Cremastocheilus has complete elytra covering and scarab beetle .

More Details

Mouthpart modifications

possess highly modified mouthparts for on : an enlarged, shield-like covering other mouthparts from below, and modified into sharp piercing appendages. are reduced, functioning only to transport liquid food.

Trichome function

Hind angles of the pronotum bear brush-like trichomes with glandular hairs secreting liquid originally thought to pacify ants; this function remains unconfirmed and the structures are not fully understood.

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Sources and further reading