1916] Thoracic and Cervical Sclerites of Insects 39 



different orders of insects and then to straighten out the con- 

 fused terminology which has been applied to them — an almost 

 impossible task. 



Straus-Durckheim, '28, believed that the thorax was 

 composed of three segments and suggested that the cervical 

 sclerites represent the remains of two segments, situated 

 originally between the head and prothorax. This suggestion 

 will be discussed under the heading. Cervical Sclerites. 



Mac Leay, '30, considered that each thoracic segment was 

 made up of four subsegments or annuli, represented in the 

 tergum by the prescutum, scutum, scutellum and postscutellum. 

 In the Zoological Jour. 1830, Vol. 5, pp. 160, he states that "owing 

 to the development of the tergum, the pectus in Hymenoptera 

 is exceedingly diminished. But were each of the sternums 

 at its maximum of development, it would also be found to 

 consist of four pieces like a tergum. This is the case in Julidae 

 and is more or less apparent in Annulosa. For instance, 

 the pectus of the prothorax in Squilla has a praesternum, 

 sternum, sternellum and poststernum. " Mac Leay leaves the 

 pleuron out of consideration. According to modern ideas his 

 view of the tergum is erroneous, since the tergum is made up 

 of but two plates, as Verhoeff, '02, Snodgrass, '09, and others 

 have proved. The anterior of these two plates is subdivided 

 into regions by sutures, these regions being termed the pre- 

 scutum, scutum and scutellum. The posterior plate is termed 

 the postscutellum. Since Mac Leay claims that the four sternal 

 plates described by him .occur in the pectus of the Julidas, 

 which are diplopods, and in Squilla, which is a crustacean, his 

 theory is not at all necessarily applicable to insects. 



Newport, '39, evidently agreed with Mac Leay regarding 

 the formation of the thoracic segments. He thought that each 

 was made up of four subsegments or annuli, represented in the 

 tergum by the prescutum, scutum, scutellum and postscutellum. 

 These annuli, he thinks are partly fused in the pleural region 

 and completely fused in the sternal region. Newport added 

 nothing new to this theory of Mac Leay's and it must be 

 regarded as untenable. Newport, however, brought forth a 

 new view pertaining to the cervical sclerites, which will be 

 referred to later. Furthermore, he is incorrect in his state- 

 ment that Audouin considered each thoracic segment to be 



