Megachile (Eurymella)

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 : 10-11

Subgenus Eurymella

Diagnosis and description.

Females: The females of most Eurymella have a distinct, robust mandible (Fig. 38 ), with tooth one markedly larger than the other teeth; the mandible is 4-toothed in Palearctic and Arabian species and divided into two plane surfaces by the outer ridge; the brushes of orange hairs in the grooves near the base of tooth one are lacking or reduced (Fig. 38 ). A complete, well-visible cutting edge is present in the third interspace (Fig. 38 ). Some Eutricharaea ( Megachile deceptoria Pérez, 1890 and a few related species; see under the subgenus Eutricharaea ) also have a robust mandible, with tooth one comparatively large, and reduced brushes of hairs near the base of tooth one (Fig. 40 ). In Eurymella , the hind basitarsus is comparatively broad, its length approximately 2.3 times its maximal width (Fig. 29 ). In Eutricharaea , the hind basitarsus is usually less broad (Fig. 28 ) (length approximately 2.7 times its maximal width), except in a few species such as M. marginata . In Eurymella the claw of the hind leg bears two thin setae (Fig. 6 ); the condition is not as clear as in Anodonteutricharaea because the basal seta is short in Eurymella . As in Eutricharaea but unlike most other group 1 subgenera, the sterna have conspicuous apical fasciae beneath the scopa in the Palearctic species. Males: Males of M. patellimana Spinola, 1838, the only Palearctic species outside the Arabian Peninsula, are easy to diagnose using the criteria mentioned in the key, especially the uniquely shaped T6 (Fig. 49 ) and the absence of inferior mandibular tooth (see below for the males of other species from the Arabian Peninsula).

Species composition.

This subgenus is diverse in Africa, where it forms numerous, morphologically distinct species groups ( Pasteels 1965); very few morphological features characterize all males of Eurymella , while the females are more homogeneous. In the Palearctic, Eurymella is probably represented by only one distinctive species, Megachile patellimana , included in the Megachile patellimana group ( Pasteels 1965). Pasteels (1979) mentions two species of the Megachile eurimera group (see Pasteels 1965) from the southern parts of the Arabian Peninsula: M. gibboclypearis Pasteels, 1979 and " M. aff. eurimera Smith, 1854".

Note.

Both Arabian species of the Megachile eurimera group are known only in the female sex, although the male of the widely distributed Afrotropical species Megachile eurimera is well known ( Pasteels 1965, Eardley 2013). The males of the Megachile eurimera group differ from those of the Megachile patellimana group in the pointed, inferior projection of the mandible and the simple T6 with preapical carina not produced posteriorly. In the present key, males of M. eurimera would run to couplet 18 ( Eutricharaea and Xanthosarus ); they differ from Eutricharaea in the strikingly different genitalia (see Pasteels 1965: p. 83), the presence of a wide, hyaline margin apically on S4 (as in Fig. 14 ), and the apical margin of T6 (beneath the preapical carina) with two teeth (as in Fig. 14 ). Xanthosarus is presumably absent from the Arabian Peninsula.

Biology.

Little is known on the biology of Eurymella ; only a brief account is given by Pasteels (1965: 127) for Megachile semifulva Friese, 1922: the nests of this species are placed in burrows in the ground and consist of leaf discs. Gess and Roosenschoon (2017) described nests of M. patellimana in the United Arab Emirates. The nests were placed in excavated burrows in compacted sand; it was not clear whether the burrows had been dug by M. patellimana or were pre-existing. A female was captured carrying a cut leaf piece, while another was captured carrying a piece of tough green plastic.

Figures

Figures 38 - 41. Female clypeus and mandibles, front view. 38 Megachile (Eurymella) patellimana 39 M. (Eutricharaea) rotundata 40 M. (Eutricharaea) deceptoria 41 M. (Eutricharaea) giraudi.

Figures 24 - 29. Female clypeus and mandibles, front view. 24. Megachile (Pseudomegachile) seraxensis 25 M. (Pseudomegachile) saussurei 26 - 29 Female hind basitarsus, lateral view 26 M. (Pseudomegachile) ericetorum 27 M. (Pseudomegachile) incana 28 M. (Eutricharaea) giraudi 29 M. (Eurymella) patellimana.

Figures 4 - 7. Claw of hind leg of females; the white lines show the basal seta; the seta is considered elongate in 4, 6 and 7 and modified to a thick process in 5. 4 Megachile (Pseudomegachile) ericetorum 5 M. (Eutricharaea) deceptoria 6 M. (Eurymella) patellimana 7 M. (Anodonteutricharaea) thevestensis.

Figures 42 - 49. Apex of male metasoma; 42 - 46, 48 T 5 - T 7 and apex of genital capsule, dorsal view 47 T 5 - T 7 and apex of genital capsule, lateral view 49 T 4 - T 6, dorsal view 42 Megachile (Megachile) melanopyga 43 M. (Pseudomegachile) sp. aff. incana 44 M. (Chalicodoma) parietina 45 M. (Chalicodoma) hungarica 46 M. (Creightonella) albisecta 47 M. (Creightonella) doriae 48 M. (Chalicodoma) manicata 49 M. (Eurymella) patellimana.

Figures 10 - 15. Male metasoma, ventral view. 10 Megachile (Eutricharaea) giraudi, metasoma with four exposed sterna, S 4 without hyaline rim, T 7 small, unmodified 11 M. (Creightonella) amabilis, metasoma with six exposed sterna, S 6 with rounded, weakly sclerotized projection 12 M. (Anodonteutricharaea) sp. aff. inornata, metasoma with four exposed sterna, S 4 with apical, hyaline rim (note that S 5 - S 8 are visible in this specimen because the metasoma has been stretched) 13 M. (Megachile) ligniseca, condition as in Fig. 12 14 M. (Eurymella) patellimana, condition as in Fig. 12 15 M. (Chalicodoma) montenegrensis, S 6 partly exposed, with rounded, weakly sclerotized projection.