1918] Thoracic Sclerites of Dissosteira 353 



region are situated the two f ureal pits "f," and the median 

 spinal pit "ssi." The f ureal pits "f" are the outward indica- 

 tions of a pair of invaginations or hollow " in-pushings " of the 

 integument serving as structures for muscle attachment. 

 These paired invaginations are called apophyses, and when their 

 basal portions unite, while their distal portions remain free to 

 form the two arms of a " Y," the structure is called the f urea or 

 forked internal structure for muscle attachment. The spinal 

 pit "ss" is the outward manifestation of an internal unpaired 

 median process called the spina, which also serves as a point for 

 muscle attachment. 



MESOTHORAX. 



Despite the fact that the fore wings are reduced to form the 

 so-cahed tegmina which are not as important as the hind wings 

 for flight, and despite the greater development of the hind legs 

 for leaping, and the consequent greater development of the 

 muscles of the metathorax, the mesothorax is subequal to the 

 metathorax in size, being but slightly smaller than the latter. 



The Mesonotum. 



In the anterior region of the mesonotum is a narrow mar- 

 ginal region "pt2" (Fig. 3) known as the pretergite. In some 

 insects it bears an internal transverse fold called the phragma, 

 to which are attached certain dorsal longitudinal muscles 

 serving to arch the notal region in the movenients of flight. 

 Immediately behind the region "pt" is an area "psco" corre- 

 sponding to the present urn of other insects, but the prescutum 

 is not demarked from the remainder of the tergal plate in the 

 grasshopper under consideration. The greater portion of the 

 tergal plate is composed of the scutum "sc2," although its limits 

 are not clearly defined in the notum of Dissosteira. The region 

 labeled "slo" is the scutelhim, and the area on either side of it is 

 known as the parascntellum or juxtascutellum, "JS2." The 

 posterior marginal area "po" is the poster gite, which is a fold- 

 like region projecting backward over the front portion of the 

 segment behind it for a considerable distance in lower insects 

 such as the Mantids, Termites, etc. With the region labeled 

 " JS2," the fold "po" is sometimes incorrectly referred to as the 

 "postscutellum," but the true mesothoracic postscntellum is 

 greatly reduced, and projects vertically downward below the 



