72 NORTH AMERICAN BLATTIDAE 



to apex of wing, without rami and with perpendicular veinlets 

 connecting with median vein weakly defined or obsolete; ulnar 

 vein weakly curved, with one to six proximal incomplete rami and 

 four to eight complete rami;i'" no intercalated triangle present. ^''^ 

 Males with median and first dorsal abdominal segments special- 

 ized, but without any distinct modification of the remaining seg- 

 ments, or with median segment alone specialized, or with all seg- 

 ments unspeclalized.i"^ Styles of male subgenital plate repre- 

 sented by slender, deflexed, similar, cylindrical processes with 

 rounded apices, the dextral slightly the longer, both entirely 

 unarmed. Armament of limbs of same character as that of Isch- 

 noptera. Cephalic femora with ventro-cephalic margin armed 

 with (usually three to six) heavy, elongate, well separated, proximal 

 spines, succeeded by a row of minute, closely set, piliform spines, 

 which is terminated distad by three heavy, elongate (in increas- 

 ing ratio) spines. Other ventral margins of femora supplied with 

 widely separated, heavy, elongate spines. A single small rounded 

 pulvillus present distad on each of the four proximal tarsal joints. 

 Small arolia present. 



The species of the present genus all have a general facies which 

 differs from that of the species of either Ischnoptera or the more 

 widely separated genus Symploce. In all but one species, P. caii- 

 delli, the females show, to different degrees, notable reduction in 

 the organs of flight. It is clear that the degree or character of 

 such reduction is valueless in determining the relationship of the 

 various species; for in many cases, species showing distinctive 

 characters which must be considered evidences of close affinity, 

 have, in the female sex, wide differences in the alar features. Such 

 reduction, however, probably affords the best means of deter- 

 mining the relative antiquity of the various species, their common 



103 Very rarely an abnormal individual of the present genus is found having no incom- 

 plete rami of the ulnar vein. Though the venation is extremely useful in determining 

 the generic position of material of the group in the large majority of cases, we must bear 

 in mind that variation is more liable to occur than in the more important features such 

 as sexual specialization or character of limb armament. 



'"■^ The tegminal and wing features naturally can not be observed in females of species 

 in which the reduction of these organs is decided. 



106 jhg remarkable character of the speciahzation of the fifth and sixth dorsal abdominal 

 segments in males of Ischnoptera is found in all the species of that genus. 



