Red-Blue Checkered Beetle

Trichodes apiarius — the red-blue checkered beetle — is one of about 3,500 species in family Cleridae (the checkered beetles). Adults are 9-15 mm long with brilliant metallic blue elytra patterned with three bold red transverse bands, plus dense fine yellow hairs across the body. The species is widespread across Europe, North Africa, and parts of western Asia. Adults are major flower-visitors and pollinators — especially on yarrow (Achillea), daisies (Asteraceae), and other open meadow composites and umbellifers. The larva, however, is a brood parasitoid of solitary bees: female checkered beetles lay eggs on flowers visited by foraging Megachile leafcutter bees; the eggs hatch into mobile first-instar larvae that attach to a foraging bee's body; the bee carries the beetle larva back to her nest in the course of pollen-collection visits; the larva detaches in the bee's nest and consumes the developing bee brood (eggs, larvae, and pollen-and-nectar provisions). The larva develops fully on the bee brood and pupates in the host nest, emerging as an adult beetle the following spring. Family Cleridae is the textbook family of bee-and-wasp brood parasitism in Coleoptera — most of the 3,500 species use similar host-hitchhiking strategies, though some related groups (like the bee wolves Trichodes group) are direct predators of adult bees on flowers. The species' ecological role is complex: as adult pollinators they are beneficial, but as larval brood parasitoids they reduce solitary bee populations, including the same Megachile species that are agriculturally important pollinators. Population dynamics are a continuing topic of pollinator-conservation research.