Megachile (Chrysosarus) rancaguensis Friese

Roig-Alsina, A. & Torretta, J. P., 2021, The leucografa species group of Megachile (Chrysosarus) (Hymenoptera: Megachilidae), Journal of Natural History 55 (7 - 8), pp. 457-470 : 467-468

Megachile (Chrysosarus) rancaguensis Friese

( Figures 1 (d), 2(e–f), 3(d–f), 5(b))

Megachile rancaguensis Friese, 1905: 137–138 (Holotype female, Chile, Rancagua , November 1903, P. Herbst, Nr. 417, ZMB, examined). Claude-Joseph 1926: 252–254. Moure et al. 2007: 1000. Montalva and Ruz 2010: 39.

Megachile (Dactylomegachile) rancaguensis: Toro 1986: 127 .

Megachile (Chrysosarus) rancaguensis: Raw 2007: 38 . Ascher and Pickering 2020.

Diagnosis. Females of M. rancaguensis are recognised by the long white vestiture all over the body. The hairs on the scutum are very long, up to 2.3× MOD. Males of M. rancaguensis are distinguished from those of M. leucografa and M. obscurior by the last flagellomere of the antenna, which is not broadened, the usually reduced group of short ferruginous setae on the forecoxa (5–7 setae up to 0.33× MOD), and the longer pubescence all over the body, the hairs on the scutum being up to 2.7× MOD, although the hairs of the outer fringe of the forebasitarsus are shorter than in the other two species.

Redescription. Female. Body length: 9.0– 10.2 mm (holotype 9.3 mm). Forewing length: 6.8–7.2 mm (holotype 7.0 mm). Colour. Integument black, except light brown base of claws. Wings weakly infuscate, with darker apices; veins and pterostigma brown. Pubescence. Hairs white around antennal sockets, on gena and on occipital margin; remainder of head with black hairs, but supraclypeal area with white (holotype) or black hairs. Mesosoma with white hairs, except black hairs on discs of scutum and scutellum, and on lateral surfaces of pronotum and propodeum; scuto-scutellar band with white hairs. Legs with white hairs, except forefemur and tibia with some intermixed black hairs. Metasoma: with entire apical bands of white hairs on T1 – T5 ; discs of T1 – T2 with white hairs, of T3 with white or black hairs (white basally and black apically in holotype), of T4 with black hairs or black and white intermixed hairs, of T5 – T6 with black hairs . Scopa with white hairs on S2–S4, white or black on S5, and black on S6. Hairs on disc of scutum 2.0–2.3× MOD, on scuto-scutellar band 0.5–1.0× MOD, on preaxilla behind tegula 1.35–- 1.55× MOD, on dorsolateral angle of pronotum 1.35–1.65× MOD, on scutellum up to 2.7× MOD, and on mesopleuron below hypoepimeral area 2.0–2.5× MOD. Hairs of apical bands on T2 – T3 0.4–0.6× MOD; discs of T2 – T4 with hairs 0.9–1.0× MOD . Sculpture. Clypeus with dense punctures, separated by shiny interspaces 0.1–0.3× PD; supraclypeal area with dense punctures and shiny interspaces laterally, but centre of area frequently feebly tessellate, with sparse punctures. Scutum and scutellum with dense punctures, separated by weakly tessellate interspaces 0.2–0.5× PD; punctures sparser around admedian lines and on centre of scutum. Punctures on mesopleuron below hypoepimeral area dense, separated by 0.2–0.5× PD. Discs of terga shiny, with dense punctures. Morphology. Inner margin of eyes convergent below, proportion of upper to lower interocular distance 1.08:1. Distance between lateral ocellus and occipital margin of head 2.0× MOD. Clypeus 2.3× as wide as long; apical margin weakly arched, smooth medially and with 2–3 poorly defined denticles on each side of middle. Maximum width of gena in lateral view 0.88× maximum width of compound eye. Proportions of scape, pedicel and first three flagellomeres 3.1:0.8:1:0.8:1; first flagellomere as long as 1.2× its apical width. Fourth mandibular tooth pointed. Hind basitarsus 2.8× as long as its maximum width. T6 slightly concave in profile, with rounded apex in dorsal view .

Male. Body length: 10.2 mm. Forewing length: 6.8 mm. Colour. Similar to that of female, except foreleg: under surface of femur and tibia, apex of tibia and entire tarsus yellowish brown; underside of second tarsomere with black ellipsoid spot. Pubescence. White hairs on most of head, except some intermixed black hairs on vertex, and brown hairs on lower part of gena; hypostomal area with dense white hairs. Mandible on lower surface with conspicuous basal tuft of dense hairs, pale brownish basally and white apically, and long hairs on lower margin. Mesosoma and legs with white hairs, except foreleg as follows: trochanter and base of femur with some yellowish hairs, basal fourth of under surface of femur separated from apical part by oblique row of setae; outer fringe of tarsus with yellowish-brown hairs (as long as 1.2–1.3× apical width of basitarsus), covered with shorter white hairs dorsally; under surface of tarsus with short white hairs. Metasoma with entire white apical bands on T1–T4; discs of T1–T3 with white hairs, of T4–T5 with intermixed white and black hairs and of T6 with black hairs; apical hairs of S1–S3 white. Sculpture. Similar to that of female. Morphology. Vertex of head broad, distance between lateral ocellus and occipital margin of head 2.3× MOD. Lower margin of mandible forming distinct angle near middle. Apical margin of clypeus with median emargination, without denticles. Maximum width of gena in lateral view 0.68× maximum width of compound eye. Hypostomal area densely pilose. Proportions of scape, pedicel and first three flagellomeres 3.4:0.9:1:1.5:1.9; first flagellomere as long as its apical width; last flagellomere not broadened. Anterior surface of forecoxa bare, with group of 5–7 ferruginous bristles up to 0.33× MOD; spine 1× MOD; lower outer margin of forefemur and tibia rounded. Forebasitarsus wide, flattened, proportion of lengths of basitarsus and second tarsomere along midline 1.0:0.9, basitarsus 1.15 as long as its apical width. Preapical carina of T6 medially with small median emargination, sometimes with 1–2 rudimentary teeth lateral to it. S5, S6, S8 and genital capsule similar to those of M. leucografa and M. obscurior .

Distribution. Chile, provinces of Cachapoal and Coquimbo ( Figure 5 (b)).

Material studied. Chile. Cachapoal: 1 F, Rancagua , November 1903, P. Herbst ( ZMB), Holotype. Coquimbo: 2 F, 1 M, Vicuña, 24 October 1966, L. Peña ( MACN).

Figures

Figure 1. (a) Megachile leucografa, female, clypeus and mandibles; (b) M. leucografa, male, ventral view showing pilose hypostomal area, tuft of hairs on inner surface of mandible (‘t’), and oblique row of hairs on under surface of femur (‘r’); (c) M. obscurior, male, ventral view showing glabrous, rugose hypostomal area; (d) M. rancaguensis, male, ventral view showing pilose hypostomal area; (e) M. leucografa, female, hind tarsus; lines indicate measurements of length and width of basitarsus; (f) M. obscurior, male, dorsal view of apical metasomal terga. Scale bars: a, e = 0.5 mm; b–d, f = 1 mm.

Figure 5. Distribution of the species of the Megachile leugografa group. (a) Megachile leucografa (triangles); (b) M. obscurior (dots); and M. rancaguensis (stars).