MORGAN HEBARD 71 



pronotum in the males, and in females which have fully devel- 

 oped tcgmina and wings, 9'-' the \cry different specialization of the 

 male dorsal abdominal segments'"" and the unspecialized deflexed 

 styles of the male subgenital plate. A much larger proportion of 

 the species also have the females showing very decided reduction 

 in the tegmina and wings. 



Scudder's genus Platamodes was based on two species, the first 

 and oldest of which we designate as genotype. 



Genotype here selected: Parcohlatta pensyhanica [Blatta pen- 

 sylvanica] (De Geer). 



Generic Description. — Pronotum weakly convex, becoming strong- 

 ly so narrowly laterad; disk very weakly impressed, with oblique 

 sulci very decided to subobsolete; caudal margin of pronotum 

 convex.'"' In females with much reduced tegmina and wings the 

 pronotum is more evenly and decidedly convex, the discal sulci 

 obsolete and the caudal margin decidedly truncate.'"- Tegmina, 

 as in Ischnoptera, with discoidal sectors (these including median 

 and ulnar veins and their branches, of which the branches of the 

 ulnar vein are the more numerous) weakly radiating, so that the 

 branches near the sutural margin are weakly oblique to that mar- 

 gin. Wings with area between the discoidal vein and anterior 

 margin broadest meso-distad, proportionately wider than in Isch- 

 noptera; mediastine vein not extending half the distance to the 

 apex of the wing, and from it spring very few of the costal veins; 

 none of the costal veins enlarged distad; discoidal vein percurrent 



3^ As in the majority of species of the Blattidae, in which the sexes show decided differ- 

 ences in the development of the organs of flight, the greatest reduction occurs in the 

 female sex. Accompanying this, a pronotal modification is almost always found, the 

 surface becoming more evenly and strongly convex and the caudal margin decidedly 

 more truncate. Thus the usual condition gives us the anomaly of the most differen- 

 tiated type (the female) being much the simplest in general structure; this being true, 

 not only for pronotum, tegmina and wings, but also for the head, abdominal segments 

 and genitalia. 



""• In bolliana and desertae alone, no specialization occurs in the male median and dor- 

 sal abdominal segments, the general facies and other features serving to place them with- 

 out question in the present genus. 



"" The pronotum and tegmina, these latter chiefly proximad, are supplied with scat- 

 tered hairs in specimens having fully developed organs of flight. In males of zebra 

 these are very numerous, but in males of bolliana the greatest abundance is found. 



"- See footnote 99, and Hebard, Trans. \m. Ent. Soc, xlii, p. 166, footnote 23, (1916). 



MEM. AM. ENT. SOC, 2. 



