324 Mr. Shuckard's Monograph of the Dorylidae, 



As in Dorylus. 



JLabrum, 



Maxillaiy 



Maxillary and 



Labial palpi, 



ThoraXy 



TegtdcB, 



Superior wings as in Dorylus, but not extending much beyond half the 

 length of the abdonoen, with one internally angulated marginal cell 

 and two submarginal cells, the first of which is considerably the longest, 

 two recurrent nervures, both of which are received by the first sub- 

 marginal cell, the first recurrent rather beyond its centre, and the 

 second near the latter, but diverging towards the apical margin of 

 the wing: the nervures of the wings very robust. 



Legs as in Dorylus. 



Abdomen elongate, clavate, much curved, the basal segment forming a 

 transverse convex posteriorly truncated peduncle j the penultimate 

 dorsal and ventral segments considerably larger than the preceding, the 

 terminal dorsal segment also largely developed, emarginate at its ex- 

 tremity, where, as well as its ventral valve and the ventral penultimate, 

 it is densely fringed with long silky down. The genital organ largely 

 developed and differing considerably from that of Dorylus. 



Type of the genus, Rhogmus firnhriatus. Shuck. 



Named from pwy^os, a fissure, in allusion to the deep emargina- 

 tion of the terminal dorsal segment of the abdomen. The claim of 

 this remarkable insect to constitute a genus is substantiated by its 

 two recurrent nervures, its very clavate abdomen, and the large de- 

 velopment of its penultimate and terminal segments. In the pecu- 

 liar emarginate structure of the latter it resembles Labidus, but in 

 that genus the emarginate portion of the segment is vertically com- 

 pressed. The very different structure of the large genital organ ex- 

 hibits an absolute necessity for its separation from Dorylus, which 

 although the general structure be the same, it is very different in 

 form, for the lateral fornicate valves (the external sheath, Burm.) are 

 widely separated and compressed flatly at their apex, where they 

 are externally and above very hairy, the hair all curled ; and within 

 at the same part they are' also flat, but glabrous and horizontally 

 truncated at the apex : the central process (the penis) is considerably 

 larger in proportion to the whole organ, vertically broader, narrow- 

 ing towards its apex, where it suddenly enlarges into a boat-shaped 

 clava, which has a deep and separating incision down its centre ; 

 the lateral processes (the inner sheath) which spring from the base 

 of the large lateral valves, and which here embrace the base of the 

 central organ, are here shorter than in Dorylus, and form large com^ 



