Mason-bee-parasite
Guides
Cacoxenus
Houdini fly
Cacoxenus is a genus of small fruit flies (Diptera: Drosophilidae) whose members are kleptoparasites of solitary bees. The best-documented species, C. indagator, infests nest cells of mason bees (Osmia spp.), laying eggs in pollen provisions intended for bee larvae. Larvae consume the pollen stores and frequently kill the host bee larvae. The common name "Houdini fly" refers to the larvae's ability to escape through mud nest partitions by gnawing exit holes. The genus has been introduced outside its native European range, including North America, where it threatens managed solitary bee populations.
Cacoxenus indagator
Houdini fly
Cacoxenus indagator is a kleptoparasitic fruit fly native to central and southern Europe that has been introduced to North America. Females lay eggs in the pollen-filled nest cells of cavity-nesting solitary bees, particularly mason bees (Osmia species). The larvae consume pollen stores intended for host bee larvae, causing host mortality or reduced adult size. The species is commonly called the "Houdini fly" for its ability to escape sealed nest cells. It poses a significant threat to managed solitary bee populations in commercial pollination operations.
Chaetodactylus claudus
Chaetodactylus claudus is a species of mite in the family Chaetodactylidae, described in 2008. It belongs to a genus known for parasitic associations with mason bees (Osmia spp.), where mites attack pollen provisions and kill bee eggs. The species has been recorded in North America.
Chaetodactylus krombeini
Krombein's hairy-footed pollen mite
Chaetodactylus krombeini is a cleptoparasitic mite in the family Chaetodactylidae that infests nests of solitary megachilid bees, primarily Osmia lignaria (blue orchard bee) and Osmia cornifrons (hornfaced bee). Described by Baker in 1962, this 0.5 mm mite consumes pollen and nectar provisions intended for developing bee larvae, causing mortality through starvation and direct egg damage. The mite disperses between nests primarily by hitchhiking on adult bees during emergence, though walking dispersal through nest entrances and parasitic wasp holes has been documented. Females are larger than males. Despite the common name "pollen mite," the species consumes more nectar than pollen.
Leucospis
Leucospis is a genus of large chalcidoid wasps in the family Leucospidae. Adults are typically 2–14 mm long with distinctive yellow and black coloration that resembles mason wasps. Females possess a uniquely curved ovipositor that arches over the back, used to drill into wood and reach host larvae in sealed cells. Larvae develop as ectoparasites on solitary bees and wasps, with typically only one parasite emerging per host cell. The genus has a global distribution in tropical and temperate regions.