Protobombus Cockerell

ENGEL, MICHAEL S., 2001, A Monograph Of The Baltic Amber Bees And Evolution Of The Apoidea (Hymenoptera), Bulletin of the American Museum of Natural History 2001 (259), pp. 1-1 : 1-

Genus Protobombus Cockerell

Protobombus Cockerell, 1908b: 326 . Type species: Protobombus indecisus Cockerell, 1908b , monobasic [also designated by Cockerell, 1909b]. Cockerell, 1909b: 9. Manning, 1960: 306. Zeuner and Manning, 1976: 231.

Chalcobombus Cockerell, 1908b: 326. Type species: Chalcobombus humilis Cockerell, 1908b [= Protobombus indecisus Cockerell, 1908b ], by designation of Cockerell, 1909b; isotypic with Protobombus Cockerell, 1908b by synonymy. Cockerell, 1909b: 11. Zeuner and Manning, 1976: 206. NEW SYNONYMY.

Sophrobombus Cockerell, 1908b: 326. Type species: Sophrobombus fatalis Cockerell, 1908b , monobasic [also designated by Cockerell, 1909c]. Cockerell, 1909c: 21. Zeuner and Manning, 1976: 213. NEW SYNONYMY.

DIAGNOSIS: Electrapine bees with a short, quadrangular metabasitarsus; similar in this respect to Thaumastobombus (described below). Protobombus differs from Thaumastobombus most notably, however, in the obtuse angle formed by the epistomal sulcus. Some Protobombus , like Thaumastobombus , have a superficial Apis ­like habitus.

DESCRIPTION: Mandible with a few, weak apical teeth. Malar space shorter than basal mandibular width. Epistomal sulcus forming obtuse angle (fig. 69). Inner margins of compound eyes parallel, not emarginate (fig. 69). F1 longer than F2, not longer than combined lengths of F2 and F3; F3 longer than F2. Preoccipital ridge rounded. Mesoscutal anterior border broadly rounded; scutellum projecting over metanotum and basal area of propodeum. Basal area of propodeum strongly declivitous. Keirotrichiate field not elevated; metatibial spur serrate or minutely ciliate; auricular basket sparse, setae short; rastellum strong and formed of stiff setae; metabasitarsus as long as wide. Margin of pterostigma within marginal cell convex; marginal cell apex offset from wing margin by pterostigma width or slightly less, apex rounded and feebly appendiculate. Sting variable, usually not barbed (some specimens appear to have microscopic barbs).

COMMENTS: The genus Sophrobombus was regarded as a genus of Meliponini by Zeuner and Manning (1976) because the forewing venation was apparently ‘‘reduced’’. The type species, Sophrobombus fatalis Cockerell , is notable for the presence of only two submarginal cells owing to the apparent absence of 1m­cu (i.e., the second transversocubital vein in Cockerell’s system) (Cocker­ ell, 1908b, 1909c). The type specimen of S. fatalis has been lost but Zeuner and Manning (op. cit.) located a specimen in the Scheele Collection (presently in the Geologisch­Paläontologisches Institut und Museum, Universität Hamburg) that matches Cockerell’s description in all respects. This specimen is here designated as the neotype for S. fatalis . The presence of only two submarginal cells is not the same ‘‘forewing venation reduction’’ as is diagnostic for Meliponini . In meliponines the distal wing veins (i.e., 2rs­m and 2m­cu) are lost, the marginal cell is typically open, and frequently other veins are also missing or greatly reduced. None of these are true for S. fatalis . The presence of a single inner metatibial spur, of an auricle, a supra­alar carina, an inner tooth on the claw, as well as numerous other characters separate this species from the Meliponini . Sophrobombus is actually an electrapine bee and similar in all respects to species of Protobombus , differing only in the number of submarginal cells. Cockerell (1908b), who did not ally this species with the stingless bees (see fig. 120), separated Sophrobombus from Protobombus by the number of submarginal cells and by the basal vein being basad cu­a in the former. Below I describe a new species ( P. basilaris ) that blends the defining characters of the ‘‘genera’’ (i.e., basal vein basad cu­a but with three submarginal cells). I have therefore placed Sophrobombus as a junior synonym of Protobombus .

Chalcobombus was differentiated from Protobombus by the shape the pterostigma as well as the third submarginal cell. The shape of the third submarginal cell varies among the species of Electrapini and, although species­specific characters can be identified, these differences in shape are not correlated with other structural characters. Similarly, the shape of the pterostigma is quite variable and was incongruent with all other characters (including the shape of the third submarginal cell!). Chalcobombus appears to be synonymous with Protobombus .