Megachile (Creightonella)

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

Subgenus Creightonella

Diagnosis and description.

The subgenus Creightonella is in many ways intermediate between the leafcutter and the dauber bees. Females: Females can easily be diagnosed by the shape and structure of the mandible (Fig. 16 ): the mandibular surface is distinct, with numerous, elongate punctures but comparatively few long ridges, and is covered by numerous hairs. The apical margin has 5 or 6 teeth, with tooth 1 broad and larger than the other teeth, and the teeth 2-5 (-6) becoming progressively smaller. There is a conspicuous, partial cutting edge in the second interspace and a small, little visible cutting edge in the third and sometimes fourth. In spite of being a leafcutter, Creightonella does not have the typical tapering metasoma of most other group 1 members and the hind basitarsus is slender (as in Fig. 26 ). The hind claw has only one elongate seta, a unique condition in Palearctic Megachile . Males: Males of Creightonella have a strong front coxal tooth and a rounded projection along the inferior margin of the mandible (Fig. 9 ). The front tarsi are unmodified although in Megachile albisecta (Klug, 1817) they are yellowish-brown (Fig. 9 ) and the second tarsal segment has a dark spot on the ventral side. The preapical carina of T6 is mostly denticulate (weakly so in M. arabica Friese, 1901) and laterally the carina extends at right angle towards the base of the tergum. T7 is mostly triangular in dorsal view, with a strong longitudinal carina (Fig. 46 ), except in M. doriae , where T7 is truncate, but with a spine on the basal part of the disc (Fig. 47 ). The apical margin of S5 is exposed in repose and the apical margin of S6 is convex and rests on the apical margin of T7 in repose (Fig. 11 ).

Species composition.

Most Palearctic species fall into a rather homogenous group of species referred to here as the Megachile albisecta group ( Metamegachile Tkalců, 1967), even if the structure of T7 is rather different in Megachile doriae ; there are at least four valid species in this group: M. albisecta , M. amabilis Cockerell, 1933, M. doriae and M. morawitzi Radoszkowski, 1876; a fifth is undescribed (A. Monfared and C. Praz, in prep). The status of M. ghigii Gribodo, 1924, described from Libya, and M. aurantiaca Rebmann, 1972 from Iran (a junior homonym of M. aurantiaca Friese, 1905) as well as of numerous Central Asian taxa related to M. albisecta remains unclear. On the Arabian Peninsula, additional species with Afrotropical affinities occur: Pasteels (1979) placed M. arabica in the aurivilli group (see Pasteels 1965) and M. felix (Pasteels, 1979), known only in the female sex, in the angulata group. Mentions of M. sudanica Magretti, 1898 from Jordan ( Zanden 1989) possibly refer to M. arabica , and both species may be conspecific ( Pasteels 1965: 26). In addition, I have seen a single specimen putatively from Yemen (BMNH) of an African species with a modified clypeus, possibly either M. bicornuta Friese, 1903 or M. cornigera Friese, 1904, both in the African Megachile cornigera group.

Biology.

The nesting biology of Megachile albisecta has been described in detail ( Ferton 1901). This species nests in burrows in the ground; whether the females dig their own burrows or rent existing cavities as suggested by Ferton is not clear, although a brief description of a nest by Grandi (1961) mentions a nest "excavated in very hard soil" [the Oriental species M. frontalis (Fabricius, 1804) consistently digs its own burrows in hard, heavy soils ( Michener and Szent-Ivany 1960, Willmer and Stone 1989]. Reports of nests in dead wood ( Benoist 1940) and in stems ( Banaszak and Romasenko 2001) are likely identification errors. Unlike the circular leaf discs cut by M. frontalis (see Michener and Szent-Ivany 1960: Plate 1), the leaf fragments used by M. albisecta are irregular; in M. frontalis , the leaf fragments used for the outer layer of the cells are also irregular ( Michener and Szent-Ivany 1960: 31 and Plate 3; Willmer and Stone 1989). In M. albisecta the fragments are stuck together by masticated leaf material, and the entire cell rests on a solid plug of masticated leaf pulp mixed with pebbles. The nest plug consists of circular leaf fragments and pebbles cemented together by masticated leaf pulp. Nests of M. albisecta do not appear to include resin according to the description by Ferton (1901), although Ferton’s subsequent articles ( Ferton 1908: 547) suggest that resin was included in the nest. Possibly the leaf pulp is hardened with secretions but not resin. Resin was not found in the nests of M. frontalis ( Michener and Szent-Ivany 1960; Willmer and Stone 1989) but was reported from the nest of the African M. cornigera ( Michener 1968). M. arabica has been observed cutting leaf discs (H. Priesner, cited in Alfken 1934). M. albisecta (and possibly all species of the Megachile albisecta group) is oligolectic on Asteraceae , with a preference for Carduoideae (C. Praz, unpublished data).

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.

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.

Figure 8 - 9. Inferior projection of male mandible. 8 Megachile (Eutricharaea) leachella, inferior projection pointed and projecting posteriorly 9 M. (Creightonella) albisecta, inferior projection rounded and directed ventrally.

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.