1922] Walker: Structure of Orthopteroid Insects 9 



polypoda (Fig. 2), two pairs of parameres, of which the smaller 

 anterior pair arises from the 8th segment in a position cor- 

 responding nearly with that of the anterior gonapophyses of 

 the female. Verhoeff ('10) also refers to both pairs of parameres 

 as the male homologues of the two pairs of female gonopods 

 (anterior and posterior gonapophyses), having abandoned his 

 earlier attempt ('03) to show that the anterior pair of parameres 

 are fused in Machilis and Lepisma to form the penis. 



Female Gonapophyses. Male Homologues. 



Ant. gonapophyses or ventral valves — true or posterior para- 

 meres, or " telopodites " 

 of seg. 9. 



Post, gonapophyses or inner valves — anterior parameres or 



"telopodites" of seg. 8. 

 (Present only in certain 

 Machiloidea). 



Lat. gonapophyses or dorsal valves — coxites of seg. 9 (gono- 



coxites), (with styli), or 

 equivalent parts of the 

 9th coxosternum. 



Male gonapophyses are not always of similar origin in the 

 various orders. In the Odonata the two plates covering the 

 genital aperture are homologues of the lateral gonapophyses 

 of the female, as shown by their development (Van der Weele, 

 "06) and are therefore vestigial coxites. 



The question as to whether the parameres of the Thysanura 

 and those of Orthopteroid insects* are homologous or not is 

 more difficult to decide. The former are primarily attached 

 to the 9th coxites, having a more or less posterior position, close 

 to the intersegmental membrane. They are thus ventral to 

 the penis. Those of Pterygote insects, in what appears to be 

 their most primitive form, arise from the walls of the penis 

 (Dermaptera), or from the same situation together with parts 

 of the intersegmental membrane (some Ephemerida), having 

 generally a lateral or dorso-lateral position, but sometimes a 

 ventral one. This difference of position throws some doubt on 

 the homologies of these structures with those of the Thysanura, 

 but such a shifting of position is by no means unusual, and as 



* These have been also termed "penis-valves," (Crampton, '20d). 



