374 PROCEEDINOS OF THE NATIONAL MUSEUM. vol. xxxii. 



lateral carinti? dull, rarely at all developed on the anterior half and then 

 very inconspicuous; median carina absent or obscurely indicated on 

 the posterior portion of the pronotuni; disk posteriorly somewhat 

 flattened or luiifornily rounded, anteriorly truncate, posteriorly 

 truncate, subtruncate or somewhat rounded. Prosternum unarmed. 

 Wing^s lateral and but little extended beyond the pronotum in the fe- 

 male, in the male overlapping above and usuall}^ extending beyond the 

 pronotum a distance equal to one-half or more than one-half the length 

 of the pronotum. Legs long, the posterior femora more than two, 

 usually three and sometimes four, times as long as the pronotum, 

 much swollen on slightly more than the basal half and armed below on 

 both margins with a few small spines; anterior tibi[« armed above on 

 the outer side alone with three or four spines or armed on both outer 

 and inner margins, the inner margin, when spined, with two to three 

 spines. Abdomen moderately full and with or without dorsal carina; 

 cerci simple in the female, in the male of various forms, armed on 

 the inner side with a tooth or projection; supraanal plate '^ small, 

 triangular and usually hidden beneath the last abdominal segment, 

 which, in the male, is apically cleft, the incision linear, V-shaped, 

 U-shaped or ])roadly rounded; subgenital plate of the female narrowly 

 cleft, of the male triangularly cleft with the lateral angles terminating 

 in apical styles. Ovipositor of various lengths, straight or curved 

 slightly upwards on downwards. 



Type. — Td'nMatus californicxLs Pictet. {^^herrnanii Thomas.) 



This is an interesting genus of apparently rare insects occurring in 

 the western and southwestern United States. Little is known of the 

 habits of the various species and some confusion has existed regard- 

 ing the status of certain forms. The synonomy of Scudder's genus 

 Cacopteris with Tdlostatus is verv certain as a type of Cacopteris, C. 

 aequalh^ has been seen and compared with the type of Idiostatus and 

 found to be generically similar. The pronotum of aequalis is as 

 angulate posteriorly and the median carina there as distinctly in- 

 dicated as in hernia /ui. 



The armature of the anterior tibioe in this genus is unusual in as 

 much as those of the two sides of a single specimen may vary, one 

 being armed above on l)oth margins and the other on the outer marghi 

 only. When long series of specimens are studied nearly all the species 

 will probably be found to exhibit more or less variation in this respect. 



As a whole Idiodatus is a very heterogeneous genus, but the various 

 types are apparently unworthy of generic distinction, their differences 

 being of insufficient importance. Three types of ovipositor, straight, 



«Scudder,'Proc. Amer. Acad. Arts Sci., XXXV, 1899, p. 87, designates what I call 

 the last aV)dominal segment as the supraiinal plate. In this matter Scudder is very 

 surely wrong, the true supraanal plate being always present but nearly or entirely 

 concealed beneath the last abdominal segment. 



