Epilobium (Pseudomegachile)

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 : 16-17

Subgenus Pseudomegachile

Diagnosis and description.

This subgenus is morphologically diverse and in both sexes few diagnostic traits are common to the entire subgenus. The description is given for the each species group. The rather distinct Pseudomegachile incana group has previously been recognized as a distinct subgenus, Parachalicodoma, but in Trunz et al.'s phylogeny ( Trunz et al. 2016), this group was nested within Pseudomegachile, with Megachile foersteri being sister to a clade formed by the Megachile cyanipennis and the Pseudomegachile incana groups. Based on its morphology, the Megachile rhodoleucura group (not included in Trunz et al. 2016) appears to build a transition between the Pseudomegachile incana and the Megachile cyanipennis groups. Similarly, the Oriental group of species previously known as Largella (considered here to form the semivestita group) is rather distinctive, although M. lanata is intermediate between the semivestita group and other, regular looking Pseudomegachile. Thus although Pseudomegachile could be split into several subgenera, numerous species are intermediate and the recognition of several subgenera does not seem practical or necessary: the number of species is not particularly large in the Palearctic or in the Oriental region, and having numerous subgenera would not be of much utility.

Species groups.

1. Megachile foersteri group: Males: Large species (body size above 15 mm) with metasoma densely covered by grey to yellow-brown vestiture. Front coxal spine present. Front tarsi modified, first tarsal segment concave inferiorly, segment 2 and 3 brownish-yellow and with black maculae on ventral surface. Mandible 4-toothed with quadrate inferior projection. Preapical carina of T6 multidentate and T7 produced into a long median tooth (Fig. 53 ). Females: Large (body size above 17 mm) and robust species with metasoma entirely covered by grey to yellow-brown vestiture. Mandibular surface comparatively dull (Fig. 23 ); mandible slightly elongate (condition intermediate between that seen in the Megachile cyannipennis and Megachile ericetorum groups), with apical margin weakly 4-toothed. Apical margin of clypeus truncate, laterally with a blunt tooth (Fig. 23 ). Ocelloccipital particularly long, nearly three times longer than the interocellar distance.

2. Megachile cyanipennis group ( Xenomegachile Rebmann, 1970): Males: Front coxal tooth present. Mandible 4-toothed (teeth sometimes blunt or small), with quadrate inferior projection. Front tarsi slightly enlarged, brownish-yellow to yellowish-white, first segment with one dark spot on ventral surface (except in Megachile cyanipennis). Preapical carina of T6 multidentate, laterally mostly without tooth (a small tooth is present in M. saussurei). T7 large, well visible from above, produced to a short spine (Fig. 52 ), or trifid, or broadly truncate. Females: Mandible comparatively short, external margin strongly rounded, apical margin 4-toothed (Fig. 24 ), although sometimes teeth nearly absent and margin almost straight (Fig. 25 ); impunctate, premarginal area along apical margin comparatively wide (Fig. 24 ). Scutellum elevated medially. Ocelloccipital distance shorter than interocellar distance.

3. Megachile rhodoleucura group: Males: As in Megachile cyanipennis group, with the following differences: front coxal tooth small; mandible without inferior projection; front tarsi unmodified although first segment with dark spot on ventral surface; T7 with apical margin emarginate medially ( Alqarni et al. 2012: Fig. 12 ). Females: As in Megachile cyanipennis group, but apical clypeal margin apically swollen, projected over base of labrum ( Alqarni et al. 2012: Figs 3 - 4 ); modified vestiture consisting of simple, short hairs on clypeus, supra-clypeal area and frons; scutellum not elevated medially.

4. Pseudomegachile incana group ( Parachalicodoma Pasteels, 1966): Males: Medium to large species (body length above 12 mm) with pale metasomal vestiture not forming distinct tergal fasciae. Front coxa without tooth. Front tarsi unmodified. Mandible 4-toothed, without inferior projection. Preapical carina of T6 multidentate, laterally with strong tooth (Fig. 43 ). T7 produced to rounded or truncate spine (Fig. 43 ). S5 partly exposed in repose (in all other groups of Pseudomegachile, S5 is hidden under S4). Females: Large, robust species (body length above 13 mm) with pale metasomal vestiture not forming distinct tergal fasciae. Mandible 5 to 6 toothed, teeth either blunt (Fig. 21 ) or acute (Fig. 22 ); width of impunctate, premarginal area along apical margin intermediate between Megachile cyanipennis and Megachile ericetorum groups. Ocelloccipital distance shorter than interocellar distance. Hind basitarsus broad, 2.7 times as long as wide (Fig. 27 ). Scutellum not elevated medially. In one species the facial vestiture is modified as in the Megachile rhodoleucura group.

4. Megachile ericetorum group: Males: Front coxa with tooth. Mandible 3-toothed, without inferior projection, although inferior margin swollen medially. Front tarsi not particularly modified although partly yellow-brown, second segment ventrally with weak, black spot. Preapical carina of T6 multidentate (Fig. 51 ). T7 produced to a median tooth that is compressed laterally (Fig. 51 ). Females: Mandible long and slender, almost as in Chalicodoma, weakly 4-toothed, impunctate area along apical margin narrow (Fig. 20 ). Scutellum not elevated medially. Clypeus flat in profile, medially produced to a small tooth (Fig. 20 ), laterally weakly denticulate. Ocelloccipital distance longer than interocellar distance.

5. Megachile flavipes group ( Archimegachile Alfken, 1933): Males: As in Megachile ericetorum group, but front tarsal segments 1-3 or 1-4 maculated ventrally, maculations sometimes reduced to thin lines. Females: As in Megachile ericetorum group, with following differences: clypeus apically without median tooth, or tooth minute; ocelloccipital distance either subequal to or shorter than interocellar distance.

6. Megachile lanata group: Males: Front coxal spine short; front tarsi unmodified. Mandible weakly 4-toothed, without inferior projection although the inferior margin is swollen medially. Preapical carina of T6 bilobed, not denticulate. T7 small, little visible. Females: Mandible as in Megachile ericetorum group, 4-toothed and comparatively elongate, impunctate area along apical margin narrow. Clypeus short, apical margin straight, without medial tooth. Ocelloccipital distance slightly shorter than interocellar distance.

Species composition.

There is only one Western Palearctic species each in the Megachile foersteri, Megachile rhodoleucura, Megachile ericetorum and Megachile lanata groups ( Megachile foersteri, M. riyadhensis, M. ericetorum and M. lanata; see above for comments on the taxonomic status of M. riyadhensis); three species in the Pseudomegachile incana group, of which two are undescribed (Dorchin and Praz, in prep.). At least M. cinnamomea Alken, 1926, M. farinosa Smith, 1853, M. flavipes Spinola, 1838, M. sanguinipes Morawitz, 1875 and M. tecta Radoszkowski, 1888 are valid species of the Megachile flavipes group; the status of M. rubripes is unclear: both M. flavipes and M. rubripes are parapatric and sculpturally very similar and have been considered as two subspecies of the same species by some authors (e. g., Özbek and Zanden 1994). At least M. cyannipennis, M. nigripes Spinola, 1838, M. saussurei, M. schnabli Radoszkowski, 1893 and M. seraxensis Radoszkowski, 1893 are valid species within the Megachile saussurei group, which includes at least three undescribed species (Dorchin and Praz, in prep).

Biology.

The nesting biology of Megachile ericetorum has been described in detail (references in Westrich 1989). Ferton (1895) provides a description of the nests, which are located in existing cavities such as existing holes in soil or clay banks, or in reed stems. The cells are arranged linearly and consist of mud; Ferton observed females gathering moist soil close to streams, a behavior not observed in bees of the subgenus Chalicodoma, which add secretions to dry mud to build their nests (see under that subgenus). The outside of the cell is coarse and irregular, while the inner wall is lined with a thin (up to 0.5 mm) layer of resin. The cell is closed with a plug of soil; the cell cap is not lined with resin on the inside of the cell, although resin is found on the outer surface, which constitutes the base of the nest cell. The nest closure consists of a layer of mud covered by a thin layer of resin, with sometimes an additional layer (2 mm) of mud. Rozen and Kamel (2007) described the biology of M. nigripes, a member of the Megachile saussurei group. The species nests in tunnels dug by the females in “adobe”, i. e., hard, dry, mud walls. The cells, oriented almost vertically in the oblique tunnels, are elongate and not arranged linearly. The cell walls probably consist of the excavated mud wall and the inside of the cell is uneven but appears to have been lined with dark coating that is "water retardant but not truly waterproof". The authors conclude that it may consist of "very fine soil particles bound together by partly dried nectar". The nests of species of the Megachile flavipes group have been briefly described several times ( Gutbier 1914, Alfken 1934, Mavromoustakis 1939, Krombein 1969). The most precise account describes the nests of M. rubripes in Turkmenistan ( Ponomareva 1958). Nests of this species were found in reed stems. Two cells were arranged linearly and made of mud "moistened with water, apparently without using secretions (...); the dry cells instantly disintegrate on submergence in water". As in M. ericetorum, the outside of the cell is irregular, but the inside is smooth; in M. rubripes resin or secretions were apparently not used to line the inner wall.

Megachile ericetorum is likely oligolectic on Fabaceae ( Westrich 1989, Müller et al. 1997), although according to Westrich (1989) Lamiaceae pollen is very occasionally also used (see also Gogala 2014). Limited evidence based on floral records suggests that M. foersteri has a preference for Carduoideae ( Asteraceae) (C. Praz, unpublished data). According to Rozen and Kamel (2007), the main host of M. nigripes in Egypt is Trifolium alexandrinum L. I observed M. saussurei on Medicago in Uzbekistan and in Iran (see also Popov 1946), M. flavipes and the closely related M. rubripes only on Fabaceae. As indicated by Alqarni et al. (2012), many unrelated species of Pseudomegachile have conspicuously modified facial hairs; these modified hairs are always found on the clypeus but may also be found on the supraclypeal area and the frons. In the species associated with Fabaceae listed above, the hairs on the face are plumose at least in fresh specimens, while in species with modified hairs, the hairs are short, simple and often bent downwards apically, or wavy (see Müller 1996). Alqarni et al. (2012) listed several species of Pseudomegachile with such modification; among the Palearctic species, they cite the following species. M. riyadhensis, which they collected exclusively on Blepharis ( Acanthaceae); I examined the pollen present in the scopa of the holotype of M. rhodoleucura (with identical facial vestiture as M. riyadhensis; see comments above) and the pollen also belongs to Acanthaceae. M. farinosa and M. cinnamomea (the condition is not clear in the latter species), both in the Megachile flavipes group also have modified facial hairs; according to my field observations, M. farinosa has a preference for the flowers of Vitex ( Lamiaceae), while M. cinnamomea is likely polylectic. In the Megachile saussurei group, Alqarni et al. (2012) cite M. transgrediens Rebmann, 1970 as having modified facial hairs; this mention likely refers to one of two undescribed species from Turkey and Iran with modified hairs ( M. transgrediens is probably a junior synonym of M. saussurei; C. Praz, unpublished); these two undescribed species are sculpturally close to M. saussurei, in fact differing from the latter in the female sex mostly by the modified facial vestiture. Host plants of these two species are unknown. M. seraxensis also has modified facial hairs; I collected one female of this species visiting Blepharis. Lastly, I collected in Israel several specimens of an undescribed species of the Pseudomegachile incana group collecting the pollen from Blepharis; this species has modified hairs on the clypeus, supraclypeal area and frons, exactly as in M. riyadhensis. Another closely related species from the Pseudomegachile incana group from Oman and the UAE has branched hairs on the clypeus; it was observed foraging on Crotalaria ( Fabaceae; Sarah Gess, pers. comm., September 2016).

Figures

Figures 50 - 53. Apex of male metasoma, dorsal view. 50 Megachile (Anodonteutricharaea) sp. aff. inornata 51 M. (Pseudomegachile) ericetorum 52 M. (Pseudomegachile) saussurei 53 M. (Pseudomegachile) foersteri.

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.

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.

Figures 2 - 3. Female mandible of Megachile (Eutricharaea) orientalis. 2 Front view; the white lines indicate the brushes of hairs in the grooves near the base of tooth 1 3 Lateral view; the cutting edge is continuous and spans the interspaces 2 - 4, although it is completely recessed behind the mandibular margin and thus not visible in front view.

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.