1909.] NATURAL SCIENCES OF PHILADELPHIA. 37 



tions, as he gives no boundaries for his two regions, other than the 

 statement that they are separated by the coxal cavities. His post- 

 sternum is apparently not the same as Meinert's, '67, and is surely not 

 the poststernum of Petri, '99, as the latter sclerite is the meron. 

 Amans' division of the sternum would be of no service in such insects 

 as Nemura, or in the Blattidae, where the coxal cavities do not divide 

 the sternum at all. On this account, and because the sternum is not 

 divided into two but into four sternites, Amans' terminology will not 

 be further considered. 



Voss, '04, states that the spini-sternum corresponds to Comstock's, 

 '02. sternellum; but, as we have seen, Comstock's, '02, sternellum is 

 the first abdominal sternum — except in the neck region, where his ster- 

 nellum and sternum are doubtless detached portions of the presternum. 

 If Comstock had found the four sternal regions, he would doubtless 

 have termed the spini-sternum the poststernellum, as he states (p. 25), 

 "A poststernellum corresponding to the postscutellum has not been 

 observed." 



The Intersegmentalia. — In front of the laterale, on either side 

 of the mesothorax of such insects as the Trichoptera, Xyelidae, etc., 

 is a sclerite which is doubtless a detached portion of the laterale. This 

 sclerite may be termed the prselaterale (fig. 18, 7 X ). Surrounding the 

 spiracle is a number of small plates, the "peritremal sclerites," and 

 between them and the pleuron of the preceding segment is a detached 

 portion of the pleuron, which may be termed the post-pleural sclerite 

 (7 P ). All of the above-mentioned sclerites will be included under 

 the general term intersegmentalia, as they lie in the intersegmental 

 membrane, more or less separated from the segment to which they 

 belong. 



Voss, '04, claims that the musculature of the first and second thoracic 

 spiracles indicates that they belong to the segment behind which they 

 are situated — that is, that the first is the prothoracic spiracle, and the 

 second is the mesothoracic one. The third spiracle Voss assigns to 

 the first abdominal segment, as do most other investigators. 



Heymons, '95, concludes from his embryological studies that the 

 spiracle does not belong to the segment preceding it, but to the segment 

 in front of which it is located. He states that in the early embryonic 

 stages, the primordia of the spiracles lie in the anterior portion of their 

 corresponding segments; as development proceeds, the spiracle ma} 7 

 migrate forward and become attached to the segment in front of it, 

 but this is only a secondary modification. 



Palmen, '77, proposed the theory that the first thoracic spiracle may 



