Chelostoma ( Chelostoma ) dolichocephalum Müller, 2025

Müller, Andreas, Pisanty, Gideon & Dorchin, Achik, 2025, Western Palaearctic Chelostoma bees of the subgenus Chelostoma (Megachilidae, Osmiini): biology, taxonomy and key to species, Zootaxa 5717 (3), pp. 329-369 : 345-347

Chelostoma ( Chelostoma) dolichocephalum Müller , sp. nov.

Holotype. IRAQ: Dahuk: Mount Gara , 1912 m, 37.015833 ° N / 43.350556 ° E, 11.5.2023, ♂ (leg. D. Baiocchi). Deposited in the Entomological Collection of ETH Zurich.

Paratypes. TURKEY: Adıyaman: Kuyucak , 8.6.1998, 1♀ (leg. M. Snizek) ; Karadut, Nemrut Dağı , 9.6.1998, 1♂ (leg. M. Halada) ; Siirt: 5 km E Eruh , 5.6.1980, 1♀ (leg. K. Warncke) . Deposited in the Entomological Collection of ETH Zurich .

Diagnosis. The females of C. dolichocephalum can be separated from those of the other two species of the C. meronense group by the following combination of characters: i) head 1.3–1.4× as long as wide ( Fig. 21 ), ii) third segment of labial palpus as long as fourth segment or slightly shorter, iii) basal area of propodeum medially distinctly longer than metanotum ( Fig. 22 ), and vi) anterior surface of coxa of fore leg medially very sparsely punctate with interspaces reaching the diameter of several punctures ( Fig. 23 ). The males differ from the two related species by the following combination of characters: i) hypostomal area with tooth-like projection of roughly triangular shape ( Fig. 24 ), ii) genal area along lower margin of compound eye distinctly impressed and almost impunctate, iii) third segment of labial palpus as long as fourth segment or slightly shorter, iv) antennal segments 5–12 asymmetrical and shorter than wide to as long as wide ( Fig. 25 ), v) last antennal segment roundish and distinctly button-like ( Fig. 25 ), vi) anterior side of antennal flagellum predominantly yellowish to yellowish-white ( Fig. 25 ), vii) basal area of propodeum medially distinctly longer than metanotum, viii) anterior margin of median projection of sternum 2 with projecting flat lamella ( Fig. 27, 28 ), and ix) patches of short black thorns of sternum 3 restricted to small spots on each side of sternal impression ( Fig. 29 ).

Description. FEMALE ( Fig. 19 ): Body length 6–7 mm. Head: Head 1.3–1.4× as long as wide ( Fig. 21 ). Distance between posterior margin of lateral ocellus and occipital margin about 1.4× as long as ocellar diameter. Clypeus rather strongly convex, its anteriormost point slightly projecting over supraclypeal area in lateral view. Punctation of clypeus laterally and apically dense with interspaces hardly exceeding diameter of one puncture and on narrow median zone more scattered with interspaces reaching diameter of two to three punctures. Supraclypeal area basally and laterally densely and medioapically sparsely punctate. Labrum about 1.75× as long as apically wide ( Fig. 21 ); its apical margin shallowly emarginate over entire width. Mandible three-toothed. Proboscis very long ( Fig. 19 ), slightly surpassing coxa of fore leg when folded; second segment of labial palpus about 5× as long as first segment and 1.55–1.65× as long as compound eye. Third segment of labial palpus as long as fourth segment or slightly shorter. Anterior side of antennal segments (8)9–11 dark reddish-brown. Mesosoma : Posterior and lateral surface of propodeum largely polished. Basal area of propodeum medially distinctly longer than metanotum, flat, crossed by numerous rather fine longitudinal carinae and bordered by narrow impunctate polished zone around its posterior margin ( Fig. 22 ). Anterior surface of coxa of fore leg medially very sparsely punctate with interspaces reaching the diameter of several punctures ( Fig. 23 ). Apical margin of tibial spur of fore leg largely truncate without or with only barely perceivable tip. Tibial spurs of hind leg yellowish to brownish. Metasoma: Marginal zones of terga 1–4 with dense and short white hair bands ( Fig. 19 ), which are usually not interrupted in fresh specimens. Terga 2–3 basally not or only weakly constricted. Scopa white, its hairs not plumose ( Fig. 19 ).

MALE ( Fig. 20 ): Body length 8–8.5 mm. Head: Head 1.1–1.15× long as wide. Distance between posterior margin of lateral ocellus and occipital margin 1.25–1.35× as long as ocellar diameter. Hypostomal carina prolonged into large tooth-like projection of roughly triangular shape in lateral view ( Fig. 24 ). Genal area along lower margin of compound eye distinctly impressed and almost impunctate. Proboscis very long, slightly surpassing coxa of fore leg when folded; second segment of labial palpus about 5× as long as first segment and about 1.35× as long as compound eye; third segment of labial palpus as long as fourth segment or slightly shorter. Antennal segments 5–12 asymmetrical with lower margin apically prolonged into acute tip and shorter than wide to as long as wide (fig. 25). Last antennal segment roundish and distinctly button-like ( Fig. 25 ). Anterior side and to different degree also posterior side of antennal segments 5–12 yellowish to yellowish-white ( Fig. 25 ); antennal segments 1–4 and 13 completely black ( Fig. 25 ). Mesosoma : Posterior and lateral surface of propodeum largely polished. Basal area of propodeum medially distinctly longer than metanotum, flat, crossed by numerous rather fine longitudinal carinae and bordered by narrow impunctate polished zone around its posterior margin. Mesosternum medioapically with narrow and almost parallel-sided impression, the margins of which are distinctly raised. Anterior surface of coxa of fore leg almost impunctate. Apical margin of tibial spur of fore leg truncate. Metasoma: Marginal zones of terga 1–5(6) with loose white hair bands ( Fig. 20 ), which are widely interrupted on terga 1–3(4). Terga 2–3 basally not or only weakly constricted. Tergum 7 basally with oval pit, laterally triangularly toothed and apically with two teeth, which are roughly parallel-sided, slightly longer than basally wide, apically (obliquely) truncate and separated from each other by semicircular incision at least three times as wide as tooth width ( Fig. 26 ). Apical margin of sternum 1 medially with semicircular incision. Median projection of sternum 2 roughly triangular in ventral view, distinctly rising towards posterior margin and composed of two parts: anterior part with projecting lamella, which is short, flat, apically rounded, separated from posterior part by distinct constriction and largely overhanging concave anterior surface of median projection ( Fig. 27, 28 ); posterior part medially with more or less shagreened and parallel-sided impression and laterally with polished margins diverging towards sternal margin ( Fig. 28 ). Sterna 2–3 lateroapically with small and well delimited tuft of short white hairs. Sternum 3 with two small spots of short black thorns on each side of apical sternal impression, which is anteriorly bordered by arched transversal swelling ( Fig. 29 ). Sternum 3 with row of stiff yellowish bristles along its apical margin ( Fig. 29 ). Sternum 4 densely covered with whitish pilosity, its apical margin with membraneous appendage that is medially divided into two upwardly curved lobes. Apical margin of sternum 5 with single row of long, yellowish and moniliform bristles ( Fig. 29 ). Sternum 6 roughly quadrangular in shape, its apical half polished, very sparsely haired and impunctate.

Distribution. Southern central to eastern Turkey, northern Iraq ( Fig. 74 ).

Pollen hosts. Unknown.

Nesting biology. Unknown, but presumably oligolectic on Lamiaceae by analogy to C. meronense .

Etymology. The species epithet refers to the long and narrow head of the female (gr. “dolichos” = long, lat. “cephalus” = head).

Figures

FIGURE 74. Distribution of the eight Chelostoma species newly described in the present publication: C. dolichocephalum (violet), C. kurdistanicum (orange), C. levantense (white), C. meronense (dark blue), C. miripalpum (light blue), C. negevense (red), C. ornithogali (yellow) and C. scabiosae (green). Made with Natural Earth (ww w.naturalearthdata.com).

FIGURES 19–29. Chelostoma dolichocephalum: 19: Female, 20: Male, 21: Head of female, 22: Basal area of propodeum of female, 23: Coxa of fore leg of female, 24: Head of male, 25: Antenna of male, 26: Terga 5–7 of male, 27: Sternum 2 of male in lateral view, 28: Median projection of sternum 2 of male in ventral view, 29: Sterna 3–5 of male.