MESOSTENUS. 215 



nearly as long as the abdomen ; tarsi shorter than the tibia?, covered, on the lower side, 

 with stiff, bristle-like hair, ending at the apex of the joints in a stiff spine, that on the 

 fourth joint being not much shorter than the claws; spurs longish, broad, acutely 

 pointed at the apex. Areolet broader than long, open at the apex. The antennae 

 are stout, nearly as long as the body, becoming thicker towards the apex ; the 

 annulus is interrupted on the lower side. 



This species is very closely allied to M. nigerrimus, Smith, but that species differs 

 in having a stouter thorax, longer antennae, in the clypeus being white at the apex, in 

 the much more gibbous scutellum, which is more abrupt behind, where it is almost per- 

 pendicular, and is also shorter compared to its breadth ; the hind legs are very much 

 longer, they being (not counting the coxae) 22 millim. in length, while those of M.pom- 

 piliformis are barely 17 millim., the length of the bodies in the two species being nearly 

 the same. The central fascia in the fore wings in M. nigerrimus is larger, extends to 

 the stigma, and is triangular in shape ; that of M. pompiliformis not extending to the 

 stigma, and being angled in the middle and broad at the top. Moreover, in M. pompili- 

 formis there are two longish depressions below the antennae, which are scarcely indicated 

 in Smith's species. 



2. Mesostenus nigerrimus. (Tab. X. fig. 20.) 



Mesostenus nigerrimus, F. Smith, Descr. of New Species of Hymen, p. 231 \ 

 Hab. Costa Kica, Cache 1 (Bogers). 



3. Mesostenus arctus. 



Mesostenus arctus, Cresson, Proc. Acad. Phil. 1873, p. 162 (g) 1 . 

 Hab. Mexico, Orizaba x (Sumichrast). 



This species may be known from the two preceding by the wings being smoky only 

 at the tips. 



B. Head, thorax, and abdomen not entirely black. (Species 4 to 45.) 



a. Abdomen black, banded with white or yellow. (Species 4 to 35.) 



1. Mesothorax entirely black. (Species 4 to 6.) 



4. Mesostenus annulitarsis. (Tab. X. fig. 15.) 



J^iger, flavo-maculatus ; clypeo, orbitis, eoxis, basi tibiarum annuloque tarsorum, flavis ; petiolo flavo, medio 



uigro. $ . 

 Long. 11 millim. ; terebra 5'5 millim. 



Hab. Panama, Volcan de Chiriqui 4000 to 6000 feet {Champion). 



Antennae longer than the body, thin, the annulus large. Head finely rugose, opaque ; 

 the orbits broadly all round, the palpi, the edge of the clypeus, and a large semicircular 

 mark above it, yellow. Thorax opaque, finely rugose, the pleurae more shining ; the 



