34 PROCEEDINGS OF THE ACADEMY OF [Jan., 



and poststernum of Meinert correspond to the regions here designated 

 as the spini- and furci-sternum. Meinert gives no description of his 

 prsB- and post-sternum, other than the brief statement that they are 

 chitinized double folds lying between the segments. Verhoeff, '04, 

 and Borner, '03, make no attempt to employ Meinert's terms in their 

 figures, but from a study of these illustrations one might hazard the 

 opinion that Meinert's presternum does not correspond to Comstock's, 

 '02, presternum at all, but is probably the furci-sternum, later 

 described. 



In all probability the presternum is merely a portion of the large 

 sternite lying behind it, and exists 'as a separate piece in but few insects. 

 It is usually the first sternite to disappear, and its small size makes it 

 of relatively tittle importance. 



The Basi-sternum. — Just behind the presternum is a large sternite 

 forming the greater part of the sternal region. This sclerite, which 

 may be termed the basi-sternum (pi. I, S 2 ), is frequently fused with 

 the anterior laterale and katepisternal complex to form the "sterno- 

 pleura" of Osten-Sacken, '84. The basi- and furci-sternum are 

 visually symmetrically divided by a longitudinal furrow — the " mid- 

 ventral" suture. 



The Furci-sternum. — Immediately caudad of the basi-sternum is a 

 somewhat smaller sternite, which bears the furca or internal forked 

 process of the sternum. On this account the sclerite in question has 

 been termed the furci-sternum. In the swiftly flying insects there is 

 usually an internal "mid-ventral lamella," or ridge corresponding to 

 the mid-ventral suture, and as this is frequently continuous with the 

 shaft of the furca, it may appear as though the base of the furcal shaft 

 arises in the basi-sternum. This, however, is only a secondary modi- 

 fication, for in the primitive forms the furci-sternum alone bears the 

 paired apophyses. Externally it is a comparatively easy matter to 

 distinguish between the basi-sternum and the furci-sternum, even when 

 these are not entirely separate sclerites, as traces of the "intrasternal" 

 suture (which separates the basi-sternal from the furci-sternal region) 

 are retained in a great number of insects. 



In the Gryllide the furci-sternum (which is very closely connected 

 with the basi-sternum) is bent inward, so that its surface forms an 

 angle with that of the basi-sternum. This bending inward of the furci- 

 sternum causes it to be concealed by the sclerites which follow it 

 and this doubtless accounts for the fact that Voss, '04, did not mention 

 this region in his description of the thorax of Gryllus. The furci- 

 sternum has been figured in the Coleoptera, but no attempt has been 



