1921] NATURAL SCIENCES OF PHILADELPHIA. 267 



The elongate triangular, pad-like, lateral tegmina of females of 

 the present species show a differentiation in this sex somewhat simi- 

 lar to that developed in /. deropeltijormis (Brunner) . These species, 

 however, do not belong to the same species group, as stated by us 

 in 1917.-'^ One striking feature of difference between the females 

 of these species is that in those of ignobilis vestigial wings are present 

 as minute pads beneath the apices of the tegmina,their very apices 

 alone sometimes projecting and scarcely extending beyond the 

 caudal margin of the metanotum. 



The Gran Chaco specimens average large for the species, all but 

 one having the pronotum solidly blackish brown. A single speci- 

 men has the pronotum dull mahogany red, becoming bay caudad; 

 the tegmina, as in the others, chestnut tinged with bay proximad. 



The individuals in the Icano series average smaller, all having the 

 pronotum solidly colored, blackish brown to chestnut brown, the 

 tegmina agreeing with the pronotum in coloration except in two, 

 which have the pronotum very dark but these organs deep chestnut. 



Ischnoptera carcarana new species. Plate XI, figures l, 2 and 3. 



This is a small species, showing, however, closer relationship to 

 the mu(^h larger /. ignohilis Saussure than to the numerous other 

 small species of the genus. 



The general coloration is darker than in ignohilis ; the limbs strik- 

 ingly bicolored, as is sometimes the case in that species. The con- 

 cealed male genitalia are distinctive, while in the brachypterous 

 males and the females the triangular lateral tegminal pads are 

 smaller than in females of ignohilis and wing pads are not present. 



A feature which we have never hitherto met with in studying the 

 Blattidae is the complete and non-intergrading dimorphism de- 

 veloped in the male sex of this species. Two males before us have 

 fully developed tegmina and wings. Three males show the general 

 contour, tegmina represented by minute lateral pads and complete 

 absence of wings, such as is true for the two females at hand. 



Though certain species are known to develop all degrees of teg- 

 minal and wing reduction, from a fully developed to a much re- 

 duced type, it would appear unlikely that intermediate conditions 

 occur in males of carcarana, so extreme and clear cut are the mac- 

 ropterous and brachypterous conditions shown. The brachypter- 

 ous type, in fact, shows for both sexes a retention in the adult con- 



31 Mem. Am. Ent. Soc, No. 2, p. 62. 



