1919] Walker: Structure of Orthopteroid Insects 283 



blades of the forceps, the movements being in the sagittal 

 plane. The inner valvulae take no part in this process, but serve 

 to roof over the path along which the eggs are passed out. 



As a type of the group we may take, the common two- 

 striped locust (Melanoplus hivittatus Say.) (Figs. 22-25). In 

 this species the eighth tergite is well developed, but the ninth 

 and tenth are not only greatly shortened, but are fused laterally, 

 the intersegmental furrow being imperfectly developed. The 

 supra-anal plate is divided by a transverse suture, the basal 

 part probably representing the eleventh tergite, while the 

 apical part is the tergite of the anal segment or telson. There 

 is also a distinct cereal basipodite, which may represent a 

 separated lateral portion of the eleventh tergite. The cerci 

 themselves are very short and unsegmented. The paraprocts 

 are broad, flat and well chitinized, and are not completely 

 separated from the tenth tergite at the lateral margin. 



The abdominal tergites are in reality pleuro-tergites, since 

 they bear the spiracles, a short distance from their lateral 

 margins. This feature is more pronounced in the Acrididae 

 than in other families of Orthoptera. The eighth sternum 

 forms a large subgenital plate and terminates in a papilliform 

 process called the "egg-guide," another characteristic Acridian 

 structure. 



The ventral valvulas are short and very stout at base, but 

 taper to a slender decurved hook-like apex. They are peculiar 

 in that the tegument is divided into five distinct sclerites, of 

 which the lateral and the three ventral ones constitute the 

 basivalvula, while the long dorsal one represents the shaft. 

 This is evident by comparison with Acrydium in which there 

 are but three sclerites. The dorsal valvulse are of about the 

 same length as the ventral, and the apices are likewise hook- 

 like, but curved upwards. They are narrowly separated at 

 base, the interval being occupied by the small superior inter- 

 valvula, which lacks the usual median apodeme, but has two 

 slight prominences for muscular attachments. 



, The superior apophyses are represented only by thin flat 

 tendons of the powerful elevator muscles of the dorsal valvulas. 

 The inferior apophyses (Fig. 24), on the other hand, are stout 

 processes which bend inwards from the base of the valvulee 

 to articulate with the inferior intervalvula. This plate has the 

 form of a curved bar, from the concave side of which a bifurcate 



