1916] Thoracic arid Cervical Sclerites of Insects 63 



The other basalar plate is probably represented by a small 

 sclerite, which is marked off on the upper corner of the precoxale 

 by a heavy suture (Fig. 3, aba2, abas). 



In Periplaneta there is a suture which divides the meso- 

 and metathoracic episternum and precoxale (Fig. 3, 0). Part of it 

 can be plainly seen and the other part (represented by the dotted 

 line) is rather faint and hard to see. If the specimen is first 

 boiled in caustic potash, the suture can be more easily distin- 

 guished. This suture suggests very strongh^ the beginning 

 of the formation of a sclerite, comparable to the anepisternum 

 (upper portion of the episternum) of the Diptera. In some 

 roaches it is represented by one heavy suture, plainly seen 

 throughout its entire length. 



Along the anterior margin of the metathoracic precoxale 

 there is marked off a small sclerite, which I shall term the 

 pre-episternum (Fig. 3, pess). It seems to be homologous with 

 Audouin's '24, "hypoteron. " Hopkins first used the term 

 pre-episternum to designate the sclerite which Audouin termed 

 the "hypoteron, " in Dytiscus and it should be applied to that 

 sclerite only. Jordan, '02, terms the pre-episternum the 

 " peristernum. " Snodgrass, '09, has used the term pre-epister- 

 num, but is so inconsistent in its application that it is hard to 

 tell what his pre-episterum represents. In his various figures, 

 he has designated the episternum, precoxale, one of the basalar 

 sclerites and the pre-episternum proper, by the term pre-epister- 

 num. In his "Thorax of the Hymenoptera, " he calls the 

 pre-episternum the "prepectus. " 



Immediately posterior to the precoxale in Periplaneta, a 

 narrow sclerite is marked off, the antecoxale of Crampton, '14, 

 whose term I shall adopt for this sclerite. This sclerite is 

 folded under the precoxale in the prothorax (Fig. 3, aci) and is 

 homologous with the lateral portion of the antecoxal piece of 

 Coleoptera. It is connected with the precoxale in Periplaneta 

 by very thin or non-pigmented chitin, not by membrane. This 

 suggests that it is probably derived from the precoxale by a 

 secondary longitudinal marking off. In other insects it has 

 either disappeared or become fused with other sclerites which 

 surround it, such as the trochantin, precoxale, etc. The 

 antecoxale was termed by Walton, '00, the "antecoxale piece;" 

 by Comstock, '02, the "second antecoxale piece," and by 

 Crampton, '09, the "antecoxale laterale. " Verhoeff, '03, 



