Callomegachile

Praz, Christophe J., 2017, Subgeneric classification and biology of the leafcutter and dauber bees (genus Megachile Latreille) of the western Palearctic (Hymenoptera, Apoidea, Megachilidae), Journal of Hymenoptera Research 55, pp. 1-54 : 8

Subgenus Callomegachile

Diagnosis and description.

In the few species present in the Palearctic, the preoccipital carina is always well developed and constitutes a good diagnostic trait. Females: Females can be recognized by the mandible without cutting edges and by the dull mandibular surface with comparatively few punctures or ridges [the mandible is also dull in some Chalicodoma of the Chalicodoma montenegrensis group, and to some extend in Megachile (Pseudomegachile) foersteri Gerstäcker, 1869 (Fig. 23 )]. The clypeus is always modified in the species of Callomegachile present in the Palearctic, either broadly truncate, with truncation wide, shiny, vertical or overhanging the base of the labrum (Fig. 18 ). Males: Males of the species present in the Palearctic always have a front coxal tooth and a quadrate projection along the inferior margin of the mandible. In many Callomegachile (but not in M. sculpturalis Smith, 1853), the first segment of the front tarsi forms a ventral concavity. The preapical carina of T6 is entire, without denticulation. The clypeus is mostly glabrous basally and with a dense fringe of hairs apically; in most other Palearctic Megachile , the clypeus is entirely covered by hairs.

Species composition.

Megachile sculpturalis , an Oriental species, has recently been introduced to western Europe ( Vereecken and Barbier 2009, Amiet 2012, Quaranta et al. 2014, Westrich et al. 2015); otherwise, only a few species of Callomegachile occur on the Arabian Peninsula, including M. simonyi Friese, 1903 and M. cephalotes Smith, 1853 among others. At least two further species occur on the Arabian Peninsula; they probably belong to previously described African species. As mentioned above, M. breviceps likely does not belong to the Palearctic fauna.

Biology.

Most species of the subgenus Callomegachile investigated so far predominantly use resin to build their nests ( Michener 2007), although other materials (wood chips, mud or even leaf fragments) are sometimes used ( Piel 1930). Megachile sculpturalis nests in existing cavities in wood and uses resin to separate the cells; the nest plug is also built with resin but sometimes covered with a thin layer of mud ( Quaranta et al. 2014, Westrich et al. 2015). Whether mud is also used for the cell partitions is unclear. In contrast, M. cephalotes appears to build entire cells with mud; the cells are placed in hollow stems ( Gupta et al. 2004). Apparently, a "brown-colored detachable membranous layer" ( Gupta et al. 2004: 58) lines the inside of the mud walls, but it is unclear what this layer refers to as it exhibits a nipple-shaped projection apically, which seems to refer to the cocoon. The floral choices of the widely polylectic species M. sculpturalis have been studied using pollen analyses ( Quaranta et al. 2014, Westrich et al. 2015).

Figures

Figures 16 - 23. Female clypeus and mandibles, front view. 16 Megachile (Creightonella) amabilis 17 M. (Maximegachile) maxillosa; the white line indicates the hypostomal tooth 18 M. (Callomegachile) sculpturalis 19 M. (Chalicodoma) hungarica 20 M. (Pseudomegachile) ericetorum 21 M. (Pseudomegachile) incana 22 M. (Pseudomegachile) sp. aff. incana 23 M. (Pseudomegachile) foersteri.