1916] Thoracic and Cervical Sclerites of Insects 73 



plates of Grylhis, Periplaneta, etc., they have designated the 

 posterior ventral cervical sclerite the " sternellum. " Con- 

 sequently it is impossible to decide to what sclerite they intend 

 the term "sternellum" to be applied. 



Snodgrass, '09, used Mac Leay's terminology for the sternum, 

 but later he used the term "eusternum" instead of "sternum," 

 to designate the verasternite, or second division of the sternum. 

 Snodgrass, '09, however, found and named only three sub- 

 divisions of the sternum, the presternum, sternum and ster- 

 nellum. The assumed poststernellum of Mac Leay is neither 

 figured nor mentioned. His claim that the presternum con- 

 sists of two plates and that it is equivalent to the "vorplatten" 

 of German entomologists is incorrect. The presternum consists 

 of only one plate in all insects in which it has been found and 

 the "vorplatten" are parts of the precoxale. Furthermore 

 in his figures, the true presternum is not shown, but in each 

 case some other part of the sternum is designated as the 

 presternum. 



Berlese, '06, considered the whole thoracic sternum as 

 composed of the pro-, aero-, meso- and metasternites. He found 

 that each of the latter was divided into two sclerites, which he 

 termed the "sterni" and "sternelli. " These subdivisions 

 (sterni and sternelli) are incorrectly homologized in the different 

 insects figured in his work. He has interpreted the "sternelli" 

 as the spinasternite, as the first abdominal segment, as the 

 spinasternite plus the furcasternite, as the verasternite, etc. 

 Hence his interpretations of the sclerites are so inconsistent 

 in his figures, that it is impossible to tell what sclerite he intends 

 to designate by his "sterni" and "sternelli." 



Intersegmentalia. Between the thoracic segments in 

 such insects as the Orthoptera, Plecoptera, Trichoptera, 

 Neuroptera, etc., there are usually a few small sclerites (Fig. 

 4, i). These vary in number, size and shape in different insects 

 and include the plates surrounding the spiracle when the latter 

 is present. They have been appropriately termed the inter- 

 segmentalia (Crampton, '09) because they are situated in the 

 intersegmental membrane. 



The intersegmentalia may be either detached portions of 

 the segment in front of them, of the segment behind them, or of 

 both. Which supposition is correct it is impossible to say, 



