Chelostoma meronense, Müller & Pisanty & Dorchin, 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

Chelostoma meronense species group

The three representatives of the Chelostoma meronense species group are characterised in both sexes by the very long mouthparts with the second segment of the labial palpus being distinctly longer than the compound eye and the proboscis surpassing the coxa of the fore leg when folded ( Fig. 19 , 30–31 , 40–41 ). They share this character with the four representatives of the C. grande species group. The females can be separated from the latter group by i) the body length, which is less than 8 mm, ii) the labrum, which is at most 2× as long as apically wide ( Fig. 21 ), and iii) the terga 2–3, which are basally not or only weakly constricted ( Fig. 30 , 40 ). The males differ by i) the apical margin of sternum 1, which is medially distinctly emarginate, ii) the median projection of sternum 2, whose apex is directed anteriorly and projecting over the sternal base ( Fig. 27 , 38 , 46 ), and iii) the sternum 3, which bears a row of stiff yellowish bristles along its apical margin ( Fig. 29 , 39 , 48 ). Due to the most probable pollen specialisation of C. meronense on Lamiaceae (see below) and the long proboscis in combination with the narrow and elongated head suggesting long-tubed flowers as hosts, the other two species of this group are likely also Lamiaceae oligoleges.

Figures

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.

FIGURES 30–39. Chelostoma meronense: 30: Female, 31: Male, 32: Head of female, 33: Basal area of propodeum of female, 34: Coxa of fore leg of female, 35: Antenna of male, 36: Head of male, 37: Terga 5–7 of male, 38: Sternum 2 of male in lateral view, 39: Sterna 2–4 of male.

FIGURES 40–48. Chelostoma miripalpum: 40: Female, 41: Male, 42: Labial palpi of female, 43: Basal area of propodeum of female, 44: Antenna of male, 45: Terga 5–7 of male, 46: Sternum 2 of male in lateral view, 47: Median projection of sternum 2 of male in ventral view, 48: Sternum 3 of male.