352 PROCEEDINGS OF THE NATIONAL MUSEUM vol. in 



Cydnidae. No other suprageneric separation occurred until Hart 

 (1919) recognized the aberrant conditions exhibited by Amnestus 

 and erected the tribe Amnestini for it. 



In evaluating the characters mentioned above, one must conclude 

 that the expanded anterior tibia is undoubtedly an adaptive feature — 

 an adaptation to a burrowing habit — and, as such, probably does 

 not deserve consideration as a prime phylogenetic indicator, though 

 it may have value as a convenient key character. The presence of 

 setigerous punctures on the submargin of the head and thorax is 

 also probably adaptive in supplying tactile hairs for the burrowing 

 habit. The narrower second tarsal segment pointed out by StM 

 (loc. cit.) probably could be construed as giving greater flexibihty 

 of the tarsus for the plant-climbing habit of the members of the 

 genus Sehirus in which it occurs, while the other forms, which are 

 chiefly burrowers, would require the stout, more rigid tarsus for 

 efficient handling of the soil. 



The present investigation to find more reliable phylogenetic indi- 

 cators resulted in the selection of certain features that have already 

 shown such value in other pentatomoids; namely, the arrangement 

 of the trichobothria on the heavily sclerotized sternites III to VII 

 (figs. 170-174) and the pattern of the venation of the posterior wing. 

 The arrangement of the trichobothria in both the nymphs and the 

 adults indicates five major groups of Cydnidae, as tabulated below: 



la. Sternites III and IV without trichobothria, V to VII each with a single 

 trichobothrium posterior to the spiracle (fig. 173) . . . . Amnestinae 

 \h. Sternites III to VII each with two trichobothria. 



2a. Trichobothria of sternites III to VII posterior to spiracles. 



3a. Trichobothria arranged in transverse pairs (fig. 171) . . . Sehirinae 



36. Trichobothria arranged in longitudinal pairs (fig. 174) . Garsauriinae 



26. Ventralmost trichobothrium of anterior sternites (or all sternites) mesad 



or anterior to spiracle. 



4a. Sternites III to VII with one trichobothrium more anterior in position 



than spiracle and one (not always strongly developed) posterior to 



it (fig. 170) Scaptocorinae 



46. Trichobothria of sternites VII and usually also of VI both posterior 

 to spiracle (fig. 172) Cydninae 



The arrangement of the trichobothi-ia on the several posterior seg- 

 ments in the Cydninae is contrary to the statement of McAtee and 

 Malloch (1931, p. 194) that Thyreocoridae and C3^dnidae "with the 

 exception of the Sehirinae, have the trichobothria longitudinally 

 arranged often nearly in line with the spiracles." The present group- 

 ing of the Cydnidae into five subfamiles can be given additional 

 support from characters drawn from the venation of the posterior 

 wing, as explained below. 



The earliest taxonomic use of the venation of the hind wing was 

 by Fieber (1861), who employed it in the first couplet in his key to 



