Callomegachile

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Megachilini
Genus: Callomegachile Michener, 1962
Subgenera: Alocanthedon, Callomegachile, Eumegachilana, Morphella
Common name: none

Overview

Callomegachile have black integument with red, yellow, tan, white, or black hair patterns (Michener 2007; Gonzalez 2008). This genus has a particularly large range in body length, from 8–39 mm, and includes the longest bee in the world, Wallace’s giant bee (Callomegachile pluto) (Michener 2007). These bees were previously considered to be a subgenus of Megachile before being elevated to the status of genus by Gonzalez et al. (2019).

Diagnostic characteristics

(modified from Michener 2007; Gonzalez 2008; Praz 2017)

  • Preoccipital carina well developed laterally.
  • Female mandible has three to seven teeth without cutting edges in the interspaces.
  • Female mandibular surface dull and mandible ridges are minutely roughened.
  • Male clypeus with a dense fringe of apical hairs and often lacking hairs basally.
  • Male front coxa with tooth or spine.
  • Male basitarsus ventrally concave.
  • Male T6 preapical carina is short, low, with a distinct concavity above the emargination.

May be confused with

Callomegachile may be confused with bees within Carinula, as they were both previously combined under Megachile (Callomegachile), and they share a number of features including the shape of T6 in males, and mandible features in females (Michener 2007; Gonzalez 2008). Male Callomegachile can be differentiated from Carinula by the distinct spine on the front coxa that Carinula lack. Female Carinula have a complete longitudinal carina medially on the clypeus (Michener 2007).

Host associations

Through observing flower-visiting behavior and pollen analysis, a number of plant families have been identified as floral hosts for Callomegachile. These include Acanthaceae, Asteraceae, Caesalpiniaceae, Fabaceae, Lamiaceae, Malvaceae, Melastomataceae, Papilionaceae, Pedaliaceae, Poaceae, Rubiaceae, and Solanaceae (Karunaratne et al. 2005; Gikungu 2006; Westrich et al. 2015; Yong et al. 2019).

Nesting behavior

Callomegachile are known to construct their nests with plant resins, sometimes exclusively and sometimes in combination with other materials, such as soils (mud, sand, and clay) and plant materials (wood fibers and leaf pieces) (Michener 2007; Westrich et al. 2015). Further, they are known to nest in pre-existing cavities in wood, plant stems, man-made structures, and nests of other species (Gupta et al. 2004; Michener 2007). The giant resin bee (Callomegachile sculpturalis) is invasive in the U.S. and has been observed removing Eastern carpenter bees (Xylocopa virginica) from their burrows to use for their own nests (Roulston and Malfi 2012). Wallace’s giant bee (Callomegachile pluto) nests in arboreal termite nests and uses resins to protect the nest cells from termites (Michener 2007).

Diversity

Callomegachile contains approximately 102 species organized within four subgenera: (Alocanthedon), (Callomegachile), (Eumegachilana), and (Morphella) (Gonzalez et al. 2019).

Known invasives

Four species are known to be invasive: Callomegachile disjunctiformis, C. rufipennis, C. sculpturalis, and C. umbripennis. All except C. disjunctiformis, an eastern Asia native observed in Europe (Italy) since 2011, have been found in the U.S. (Michener 2007; Genaro 2008; Bortolotti et al. 2018).

C. rufipennis, native to Africa, is adventive to the Caribbean islands, including the U.S. territory of Puerto Rico and U.S. Virgin Islands (Michener 2007; Genaro 2008; Bortolotti et al. 2018).

C. sculpturalis, native to eastern Asia, was first identified in the U.S. in 1994 in North Carolina (Magnum and Brooks 1997). Their range has continued to expand across the east coast and spread westward to Kansas (Hinojosa-Díaz 2008). They have also been reported in Europe (in France, Italy, Switzerland, Germany, and Hungary) since 2008 (Bortolotti et al. 2018).

C. umbripennis, native to southern Asia, has been observed in several U.S. states, including Florida, New Jersey, and Hawaii (Bortolotti et al. 2018).

Distribution

Callomegachile is a widely distributed subgenus (Michener 2007). Their native range includes southern Africa, southwestern to southeastern Asia, northern Australia and islands in the Indian and South Pacific Oceans, including Mauritius, New Hebrides, and New Caledonia (Michener 2007). Callomegachile species have been introduced in Europe and several areas of the Americas, including the U.S. (Michener 2007; Genaro 2008).

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

<p><em>Callomegachile sculpturalis</em> female face, photo: Colleen Meidt</p>
Callomegachile sculpturalis female face, photo: Colleen Meidt
<p><em>Callomegachile sculpturalis</em> female lateral habitus, photo: Colleen Meidt</p>
Callomegachile sculpturalis female lateral habitus, photo: Colleen Meidt
<p><em>Callomegachile sculpturalis</em> female abdomen, photo: Colleen Meidt</p>
Callomegachile sculpturalis female abdomen, photo: Colleen Meidt
<p><em>Callomegachile sculpuralis </em>male face, photo: Shaun Heller</p>
Callomegachile sculpuralis male face, photo: Shaun Heller
<p><em>Callomegachile sculpuralis </em>male lateral habitus, photo: Shaun Heller</p>
Callomegachile sculpuralis male lateral habitus, photo: Shaun Heller
<p><em>Callomegachile sculpuralis </em>male abdomen, photo: Shaun Heller</p>
Callomegachile sculpuralis male abdomen, photo: Shaun Heller
<p><em>Megachile cephalotes</em> female tarsal claw, photo: Joshua Hengel</p>
Megachile cephalotes female tarsal claw, photo: Joshua Hengel