100 PROC. ENT. SOC. WASH., VOL. 22, NO. 5, MAY, 1920 



sternites "e?" and "e ;i " (Fig. 1) occur in the mesothorax and 

 metathorax of the Grylloblattidae and Isoptera, although they are 

 also found in the Embiidae and certain other forms related to 

 the Plecoptera. The sclerites of the pleural region in general are as 

 much like those of the Isoptera as any insects, but they also 

 present certain features suggestive of the Dermaptera and other 

 insects related to the Plecoptera as well. 



With regard to the appendages of the thorax, we find in them 

 also, a curious combination of features present in several other 

 group of insects. The coxae, "ca" (Fig. 1) resemble those of the 

 Grylloblattidae very markedly, but the other portions of the legs 

 resemble those of certain immature Plecoptera and the wingless 

 Psocidae in many respects. The reduction of the number of tar- 

 sal segments is a feature found in certain higher insects (Hemip- 

 tera, Thysanoptera, etc.) related to the Psocidae; but there is also 

 a tendency toward such a reduction, in the immature Plecoptera 

 and their allies. The wings, as figured by Mr. Caudell, appear 

 to be much like those of certain Psocids and Embiidae (which 

 are related to the Plecoptera), but they also present many points 

 of resemblance to the Isoptera particularly in the breaking off 

 of the wings near the base (a feature which seems to be peculiar 

 to the termites and certain Blattids), as Mr. Caudell has pointed 

 out. I find something vaguely suggestive of the wings of certain 

 Psocids and Thysanoptera in the Zoraptera; but I am not suffi- 

 ciently familiar with the venation of the insects related to the 

 Psocidae (i. e., the Thysanoptera, Hemiptera, etc. and possibly 

 the Strepsiptera also), to be able to tell which of these insects 

 approaches the Zorapteron type the most closely in their venation. 



There are two types of individuals in the blind, apterous 

 "caste" of the Zoraptera. In one type (Fig. 2), which I have 

 interpreted as the male form (since it has genitalia very sugges- 

 tive of those of the male Mantidae) there is one less ventral 

 plate than in the forms I have interpreted as the females, the 

 ventral plate labeled "hp" in Fig. 4 of the female, being either 

 not developed, or not sufficiently strongly chitinized and pig- 

 mented to be visible in the males (Fig. 2). 



In some males, the genitalia were retracted beneath the plate 

 labeled "ha" in Fig. 2, so that only their tips protruded behind 

 its margin; but the specimen from which Fig. 2 was drawn was 

 chosen to illustrate the exserted condition of the parts, since they 

 seem to be better developed in such specimens. From the some- 

 what more developed condition of the parts, and from the fact 

 that they are marked extruded, I would regard such forms as 

 sexually mature, despite the fact that they are apterous; but, of 

 course, the extruded condition of the genitalia may have been 



