GENERIC SYNONYMY. 11 



are four-jointed. The mouthparts of the female are chitinized and 

 projecting, being adapted for piercing; the male has the mouthparts 

 much more rudimentary. 



The thorax is peculiarly formed, and the most remarkable feature 

 about it is the very great development of the scutum and the conse- 

 quent reduction of the prescutum. The diagram given on Plate I, 

 figure 1, will serve to show this clearly. The presence of such a large 

 membranous field on the pleura* is also remarkable. The mesonotum 

 has always a surface covering of pilosity, which varies in color and 

 also very much in distribution and in form in the different species. 

 These characters are of considerable importance and are extensively 

 used in this paper. There is a group of hairs situated on the upper 

 portion of the mesopleura between the wing base and the base of the 

 haltere, which is throughout this paper referred to as the 'pleural tuft. 

 Immediately behind the posterior spiracle there is an area which 

 sometimes bears hairs; this I have called the post-spiracular area. 



The abdomen has been considered as consisting of from seven to 

 nine segments by various authors, and though I have always found 

 eight present there is, besides this number, a loose, scale-like appen- 

 dage at the base, which most authors consider as the basal abdominal 

 segment. I am not certain of the homology of this part, and while 

 I consider it really abdominal (as against thoracic), I have in this 

 paper consistently referred to it as the hasal scale., and considered the 

 abdomen as possessing, in addition to this, eight distinct segments. 

 No work has been done with the genitalia in this group and, owing to 

 the nature of these organs, it would require very careful work and 

 plenty of fresh material to make a successful study of them. They 

 are not normally so situated as to be of use in identifications. 



The legs are strong, and the tarsi generally well developed, the 

 fore and hind pairs being generally broad and the metatarsi very 

 much elongated. The last three tarsal joints are as shown on Plate 

 V, figure 10. In most species there is an extension at the apex of the 

 hind metatarsus, and in the species with this process there is generally 

 a corresponding modification of the second joint, which is explained 

 in my remarks on the genera. The claws of the male are trifid, of the 

 female simple, bifid, or with subbasal tooth. The wings are very 

 broad and the venation is peculiar, resembling Scatopse in some re- 

 spects. (For venation see PI. I, figs. 1—4.) 



GENERIC SYNONYMY. 



The generic name Simidiuni was created by Latreille ^ with one 

 species included. This species, Rhagio colomhascJiensis Fabricius, 

 must be accepted as the type even though Latreille in volume 14 of 

 the same publication (1805. p. 294) indicates that this species, in his 



1 nist. Xnt. Crust, .t Ins;., vol. .■?, 1802, p. 426. 



