Coelioxys

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Megachilini
Genus: Coelioxys Latreille, 1809
Subgenera: Allocoelioxys, Austrocleptria, Boreocoelioxys, Callosarissa, Coelioxys, Cyrtocoelioxys, Dasycoelioxys, Eingana, Glyptocoelioxys, Leuraspidia, Liothyrapis, Melissoctonia, Neocoelioxys, Paracoelioxys, Platycoelioxys, Rhinocoelioxys, Rozeniana, Synocoelioxys, Torridapis, Xerocoelioxys
Common name: cuckoo bees

Overview

Coelioxys are black to dark brown bees that range in body length from 5–22 mm. Intraspecific variation can be high, with color and structural characters usually of value in identification between individuals in addition to large variations in adult body size (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Sometimes the abdomen has reddish areas with pale apicalapical:
near or at the apex or end of any structure
hair bandsbands:
usually referring to bands of hair or bands of color that traverse across an abdominal segment
on the tergaterga:
the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
(Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). The thorax is black and usually possesses axillaaxilla:
the triangular or rounded point on the thorax where thoracic muscles meet the forewing of an insect
that are angled or protruding as a spine. Overall, there is a reduction in hair across the body. Females are easily recognized by their pointed abdomen and lack of scopae (Droege 2015Droege 2015:
Droege, S. 2015. The Very Handy Manual: How to Catch and Identify Bees and Manage a Collection. USGS Native Bee Inventory and Monitoring Lab ( https://www.pwrc.usgs.gov/nativebees/Handy%20Bee%20Manual/The%20Very%20Handy%20Manual%20-%202015.pdf ).). T6T6:
the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
of the male is usually ornamented with an arrangement of knobs, teeth, or spikes (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Diversity

Coelioxys consists of over 500 species in 20 subgenera worldwide; around 45 species in 9 subgenera in the United States and 10 species in Canada (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). A recent revision expanded the number of world subgenera from 15 to 20 (Rocha-Filho and Packer 2016Rocha-Filho and Packer 2016:
Rocha-Filho, L.C. and L. Packer. 2016. Phylogeny of the cleptoparasitic Megachilini genera Coelioxys and Radoszkowskiana , with the description of six new subgenera in Coelioxys (Hymenoptera: Megachilidae). Zoological Journal of the Linnean Society (2016: to be updated). DOI: 10.1111/zoj.12484).

Diagnostic characteristics

(modified from Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.)

• Arolia absent.
• Axillae almost always produced posteriorly to an angle or spine.
• Eyes with abundant hair.
• Metanotum metanotum:
  the posterior dorsal segment of the thorax, behind the scutellum
  without median tooth or tubercletubercle:
  a small knob-like or rounded protuberance
  .
• Omaular carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  present.
• Stigma stigma:
  a pigmented/ thickened spot on the costal margin of the forewing, usually at the end of the radius(Greek, stigma= mark)
  twice as long as broad or more.
• Female scopascopa:
  modified hairs for carrying pollen; often branched and dense hairs on the hind-leg, or on the ventral surface of the abdomen in Megachilidae
  absent.
• Female tarsal claws simple.
• Male T6T6:
  the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
  with two pairs of long preapicalpreapical:
  referring to a section of a bee that is physically found just before the outermost (or apical) end of the section or segment
  spines.

May be confused with

Coelioxys may be confused with species in the genera Radoszkowskiana due to tapering of the abdomen after the second segment in females, lack of scopascopa:
modified hairs for carrying pollen; often branched and dense hairs on the hind-leg, or on the ventral surface of the abdomen in Megachilidae
, and presence of preoccipital carinacarina:
a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
on the side of the head (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Coelioxys can be differentiated from Radoszkowskiana based on the combination of distinguishing characteristics listed above. In addition, as larvaelarvae:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
Coelioxys can be differentiated from Radoszkowskiana by the curvature of the first instar’s mandibles: Radoszkowskiana curve orally, while Coelioxys bend caudally (Rozen and Kamel 2008Rozen and Kamel 2008:
Rozen, J.G., Jr. and S.M. Kamel. 2008. Hospicidal behavior of the cleptoparasitic bee Coelioxys ( Allocoelioxys ) coturnix , including descriptions of its larval instars (Hymenoptera: Megachilidae). American Museum Novitates 3636: 1ndash;15.).

Coelioxys may be also confused with Dioxys due to similar appearance, with females having reduced scopal hairs and a pointed abdomen with black and white banding. However, Coelioxys lacks the medial spine on the metanotummetanotum:
the posterior dorsal segment of the thorax, behind the scutellum
that is present in Dioxys (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Known invasives

Coelioxys coturnix, a native of the Mediterranean, southwestern Europe, North Africa, and India was first noticed in the United States in 2000. It was unintentionally introduced to the U.S., and has been found in Maryland, Washington, D.C., southern New England, and southern Pennsylvania. Its presumed host in the U.S. is Megachile rotundata (Droege 2015Droege 2015:
Droege, S. 2015. The Very Handy Manual: How to Catch and Identify Bees and Manage a Collection. USGS Native Bee Inventory and Monitoring Lab ( https://www.pwrc.usgs.gov/nativebees/Handy%20Bee%20Manual/The%20Very%20Handy%20Manual%20-%202015.pdf ).).

Host associations

Female Coelioxys do not gather pollen from flowers since the larvaelarvae:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
develop parasitically on their host’s pollen provisions (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). It is presumed that wide varieties of flowers are used for nectar.

Nesting behavior

Coelioxys are one of the various groups of solitary brood parasites collectively referred to as “cuckoo bees” or cleptoparasites. Most known hosts are Megachile (Droege 2015Droege 2015:
Droege, S. 2015. The Very Handy Manual: How to Catch and Identify Bees and Manage a Collection. USGS Native Bee Inventory and Monitoring Lab ( https://www.pwrc.usgs.gov/nativebees/Handy%20Bee%20Manual/The%20Very%20Handy%20Manual%20-%202015.pdf ).), but a few are known to parasitize orchid bees and cavity-nesting species of Centris. After a host nest is found, a small, curved, specialized egg is laid inside a host cell that is being provisioned by the host female, or is injected through a slit made into the cell after it has been sealed off (Baker 1971Baker 1971:
Baker, J.R. 1971. Development and sexual dimorphism of larvae of the bee genus Coelioxys . Journal of the Kansas Entomological Society 44: 225ndash;235.). Eggs may be placed near or on host eggs, oviposited through the pollen provisions, or stuck between pieces of leaf that make up the cell wall (Scott et al. 2000Scott et al. 2000:
Scott, V.L., S.T. Kelley, and K. Strickler. 2000. Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 93: 941ndash;948.). Unlike most bee larvaelarvae:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
, they are active and develop a sclerotizedsclerotized:
hardened by the formation of sclerotin, specifically the exoskeleton of an insect
head bearing extended sickle-shaped mandibles that may be further modified with secondary spines or prongs (Baker 1971Baker 1971:
Baker, J.R. 1971. Development and sexual dimorphism of larvae of the bee genus Coelioxys . Journal of the Kansas Entomological Society 44: 225ndash;235.; Rozen and Kamel 2008Rozen and Kamel 2008:
Rozen, J.G., Jr. and S.M. Kamel. 2008. Hospicidal behavior of the cleptoparasitic bee Coelioxys ( Allocoelioxys ) coturnix , including descriptions of its larval instars (Hymenoptera: Megachilidae). American Museum Novitates 3636: 1ndash;15.). The mandibles are used to kill the host egg or larvalarva:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
. The larvalarva:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
has a “ hospicidalhospicidal:
the early instars of clepoparasitic bees, which have been oviposited into complete brood cells of another species. When the early instars develop, they kill off the developing individual that was originally occupying the brood cell.
” body form temporarily before molting into a more ordinary grub-like form (Rozen and Kamel 2008Rozen and Kamel 2008:
Rozen, J.G., Jr. and S.M. Kamel. 2008. Hospicidal behavior of the cleptoparasitic bee Coelioxys ( Allocoelioxys ) coturnix , including descriptions of its larval instars (Hymenoptera: Megachilidae). American Museum Novitates 3636: 1ndash;15.). If more than one egg is laid by the parasitic female, the hatched larvaelarvae:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
will destroy sibling eggs as well as the host’s egg (Baker 1971Baker 1971:
Baker, J.R. 1971. Development and sexual dimorphism of larvae of the bee genus Coelioxys . Journal of the Kansas Entomological Society 44: 225ndash;235.; Scott et al. 2000Scott et al. 2000:
Scott, V.L., S.T. Kelley, and K. Strickler. 2000. Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 93: 941ndash;948.). Subsequently, it feeds on the pollen stores of its host (Scott et al. 2000Scott et al. 2000:
Scott, V.L., S.T. Kelley, and K. Strickler. 2000. Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 93: 941ndash;948.).

Distribution

Coelioxys is distributed worldwide, with high species diversity in South America, and relatively little diversity in Australia. In North America, they are found transcontinentally, from the Arctic to Florida, in a wide variety of habitats (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.).

​Distribution map generated by  Discover Life -- click on map for details, credits, and terms of use.

References

Baker, J.R. 1971. Development and sexual dimorphism of larvaelarvae:
active immature form of an insect, especially one that differs greatly from the adult and forms the stage between egg and pupa
of the bee genus Coelioxys. Journal of the Kansas Entomological Society 44:225-235.
 
Droege, S. 2015. The Very Handy Manual: How to Catch and Identify Bees and Manage a Collection. USGS Native Bee Inventory and Monitoring Lab (https://www.pwrc.usgs.gov/nativebees/Handy%20Bee%20Manual/The%20Very%20Handy%20Manual%20-%202015.pdf)
 
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.
 
Rocha-Filho, L.C. and L. Packer. 2016. Phylogeny of the cleptoparasiticcleptoparasitic:
bees that lay their eggs in the nest cells of bees in other genera. Their larvae depend on the pollen provided by their host. Since cleptoparasitic bees don't provision their own nests, and instead depend on the pollen collected by their host, the females lack pollen collecting hairs. This often gives them a wasp-like appearance.
Megachilini genera Coelioxys and Radoszkowskiana, with the description of six new subgenera in Coelioxys (Hymenoptera: Megachilidae). Zoological Journal of the Linnean Society (2016: to be updated). DOI: 10.1111/zoj.12484
 
Rozen, J.G., Jr. and S.M. Kamel. 2008. Hospicidalhospicidal:
the early instars of clepoparasitic bees, which have been oviposited into complete brood cells of another species. When the early instars develop, they kill off the developing individual that was originally occupying the brood cell.
behavior of the cleptoparasiticcleptoparasitic:
bees that lay their eggs in the nest cells of bees in other genera. Their larvae depend on the pollen provided by their host. Since cleptoparasitic bees don't provision their own nests, and instead depend on the pollen collected by their host, the females lack pollen collecting hairs. This often gives them a wasp-like appearance.
bee Coelioxys (Allocoelioxys) coturnix, including descriptions of its larval instars (Hymenoptera: Megachilidae). American Museum Novitates 3636:1-15.
 
Scott, V.L., S.T. Kelley, and K. Strickler. 2000. Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 93:941-948.
 
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North America’s Bees. Princeton University Press, Princeton and Oxford, 288 pp.