Genus: Dioxys Lepeletier & Serville, 1825
Common name: cuckoo bees
Dioxys are black bees with white apical bands on the terga that range in body length from 6–12 mm (Michener 2007). Dioxys are cleptoparasitic bees, and the females lack scopa because they do not gather pollen (Michener 2007). They also have a noticeably pointed abdomen (Wilson and Carril 2016). The narrowed body shape, coloration, and reduced setae give them a slightly “waspy” appearance, like many other cleptoparasitic bees.
Dioxys contains 15 species worldwide; 5 of which occur in the U.S. and Canada (Michener 2007).
(modified from Michener 2007)
Dioxys is similar in appearance to the other Dioxyini, but can be distinguished by the combination of characters above (Michener 2007).
There are no known invasives.
Dioxys are cleptoparasitic bees, and females do not gather pollen from flowers since the larvae develop parasitically on their host’s pollen provisions (Michener 2007). They will, however visit a wide variety of flowers for nectar. Dioxys are known to parasitize bees in several different genera within the Megachilinae subfamily (Hurd 1958). Dioxys aurifuscus has been observed in the nests of Anthidium (Cockerell 1909; Hicks 1929). Dioxys pomonae has been associated with Anthidium, Megachile, and Osmia (Hurd 1958). Dioxys producta is also a parasite of multiple species of Anthidium (Hurd 1958).
Dioxys are one of the various groups of solitary brood parasites collectively referred to as “cuckoo bees” and are cleptoparasitic on other megachilid bees. They prefer parasitizing Anthidium, Megachile, and Osmia nests, although the boundaries of host selection within these groups are little understood (Michener 2007). The female parasite often spends time around the preferred floral resources of its host to locate them. Once a host nest is found, an egg is laid inside a cell as it is being provisioned by the host female (Rozen and Favreau 1967), or it is injected into the cell after it has been sealed off (Rozen and Özbek 2005). Unlike most bee larvae, they are active after hatching from the egg. They have pointed mandibles that are used to destroy the host egg or larva (Rozen and Özbek 2004). The larva retains the somewhat modified “hospicidal” body form for multiple instars before molting into a more ordinary grub-like form where it feeds on the pollen stores of its host (Rozen and Özbek 2004).
Dioxys has a wide distribution in the Palearctic as well as North America, where Dioxys occupies much of the western U.S. (Michener 2007).