Chelostoma (Gyrodromella) tonsum Müller, 2015

Müller, Andreas, 2015, Palaearctic Chelostoma bees of the subgenus Gyrodromella (Megachilidae, Osmiini): biology, taxonomy and key to species, Zootaxa 3936 (3), pp. 408-420 : 414-415

Chelostoma (Gyrodromella) tonsum Müller , spec. nov.

Holotype. TURKEY, Adiyaman: Kuyucak, 8.6.1998, ♂ (leg. M. Halada). Deposited in the Entomological Collection of ETH Zurich.

Paratypes. TURKEY, Adiyaman: Kuyucak, 8.6.1998, 2♂ (leg. M. Halada, M. Snizek); Karadut, 50km NE of Adiyaman, 1000 m, 1.6.2001, 2♀, 1♂ (leg. K. Denes); Bingöl: Buglan Gecidi, 40 km NW of Mus, 1600m, 27.5.2010, 1♂ (leg. M. Halada); Hakkari: W of Uludere, 17.5.1975, 3♂ (leg. K. Warncke); 25 km SW of Hakkari, 1200 m, 31.5.1980, 1♂ (leg. M. Schwarz); 30 km SW of Hakkari, 1150 m, 1.6.1980, 1♂ (leg. M. Schwarz); Semdinli, 1700 m, 12.6.1981, 3♂ (leg. K. Warncke); S of Beytüssebap, 1300 m, 13.6.1984, 4♀, 4♂ (leg. K. Warncke); 5 km N of Oramar, 1500 m, 16.6.1984, 1♀, 3♂ (leg. K. Warncke); Mardin: Midyat, 900 m, 15.5.1983, 2♂ (leg. K. Warncke); Siirt: 20 km NW of Sirnak, 1500 m, 5.6.1980, 1♂ (leg. M. Schwarz). Deposited in the Entomological Collection of ETH Zurich, the Oberösterreichische Landesmuseum Linz and the private collection of M. Schwarz (Ansfelden).

Diagnosis. The female is morphologically identical to the female of C. rapunculi ; in most cases, however, its smaller body length not exceeding 7mm allows its separation from the larger C. rapunculi , whose body length is rarely below 7.5mm. The male differs from all species of the rapunculi species group except C. clypeale by the uninterrupted comb of long bristles at the apical margin of sternum 5 in combination with the widely spaced and more or less parallel-sided upper lateral teeth of tergum 7 ( Fig. 9 ). In contrast to C. clypeale , the distance between the spots of black bristles at the apical margin of sternum 3 is as wide as the maximal spot width or wider ( Fig. 10 ), sternum 4 has small lateroapical tufts of yellowish bristles, the pilosity along the lower genal area is sheared in appearance and very short behind the mandibular base ( Fig. 8 ), the projecting apex of the upper lateral teeth of tergum 7 is slightly wider than long ( Fig. 9 ), the lower median tooth of tergum 7 is of trapezoidal rather than triangular shape ( Fig. 9 ), and the membraneous appendage of sternum 4 is about as long as to slightly longer than the length of tarsal segment 3 of the hind leg.

Description. FEMALE: Body length 6.5–7 mm. Apart from the smaller body size morphologically identical to C. rapunculi .

MALE: Body length 6.5–8mm. Head: Head about 1.1x as long as broad. Second segment of labial palpus about 4x as long as first segment. Pilosity along lower genal area straightly sheared and short, hairs just behind mandibular base half as long as length of first segment of labial palpus ( Fig. 8 ). Distance between lateral ocellus and preoccipital ridge slightly less than 2x as long as ocellar diameter. Preoccipital ridge raised to a very short carina. Mesosoma: Punctation of scutum rather scattered with interspaces reaching the diameter of two, rarely three punctures. Scutellum more densely punctured with interspaces usually not exceeding the diameter of half a puncture except medially where the punctation is more scattered. Basal zone of propodeum sloping, half as long as metanotum and with more or less distinct longitudinal ridges. Metasoma: Anterior surface of tergum 1 shallowly concave. Punctation of tergal discs 1–5 moderately dense, interspaces varying in size between the diameter of half a puncture and the diameter of two, rarely three punctures. Punctation of marginal zones of terga 1–5 slightly finer and distinctly denser than on discs. Tergum 6 densely punctured with interspaces rarely exceeding the diameter of one puncture. Bases of terga 2–4 distinctly constricted. Terga 1–3(4) with dense and medially interrupted apical white hair bands. Tergum 7 with large, deep and polished pit surrounded by two widely spaced and more or less parallel-sided upper lateral teeth, whose projecting apex is slightly wider than long, and one small lower median tooth, which is of trapezoidal shape ( Fig. 9 ). Median elevation on sternum 2 triangular in profile, its posterior surface evenly sloping, half-elliptical in shape and almost flat. Sternum 3 medioapically with two oval spots of black bristles, which are separated from each other by a distance equal to or slightly longer than maximal width of spot ( Fig. 10 ). Sternum 4 with small lateroapical tufts of yellowish bristles. Membraneous appendage of sternum 4 about as long as to slightly longer than tarsal segment 3 of hind leg. Apical margin of sternum 5 with uninterrupted comb of long yellowish bristles.

Distribution. Eastern Turkey; westernmost record: Kuyucak (Adiyaman province).

Pollen hosts. Probably oligolectic on Campanula (Campanulaceae) and possibly also closely related genera (based on the microscopical analysis of 3 pollen loads from the same locality).

Nesting biology. Unknown.

Etymology. tonsus = sheared, referring to the short pilosity along the lower genal area of the male.

Figures

FIGURE 5 – 10. 5: Chelostoma clypeale, head of female. 6: Chelostoma clypeale: terga 4 – 7 of male. 7: Chelostoma clypeale, sterna 2 – 4 of male. 8: Chelostoma tonsum, head of male. 9: Chelostoma tonsum, terga 4 – 7 of male. 10: Chelostoma tonsum, sterna 2 – 3 of male.