THE EXTERNAL ANATOMY OF INSECTS 



51 



The parapsides. In some Hymenoptera the scutum of the meso- 

 thorax is divided into three parts by two longitudinal sutures. The 

 lateral portions of the scutum thus separated from the mesal part are 

 termed the parapsides. 



The sclerites of the pleura. In the accompanying figure (Fig. 61) 

 the sclerites of the left pleurum of a wing-bearing segment are repre- 

 sented diagrammatically ; these sclerites are the following: 



The episternum. Each pleurum is composed chiefly of two 

 sclerites, which typically occupy a nearly vertical position, but 

 usually are more or less oblique. In most insects the dorsal end of 

 these sclerites extends farther forward than the ventral end, but in 

 the Odonata the reverse may be true. The more anterior in position 

 of these two sclerites is the episternum (Fig. 61, Eps), 



In several of the orders of insects one or more of the episterna are 

 divided by a distinct suture into an upper and a lower part. These 

 two parts have been designated by Crampton ('09) as the anepistSr- 

 num and the katepisternum respectively (Fig. 62). 



The epimerum. The epimerum is the more posterior of the tw 

 principal sclerites of a pleurum (Fig. 61). It is separated from the 

 episternum by the pleural suture (Fig. 61, PS) which extends from the 

 pleural wing process above (Fig. 61, \Vp) to the pleural coxal process 

 below (Fig. 61, CxP). 



In some of the orders of insects one or more of the epimera are 

 divided by a distinct suture into an \\\ >p,>r and a 

 lower part. These two parts have been desig- 

 nated by Crampton ('09) as the auepiineniin 

 and the katepimerum respectively (Fi.L 1 . 6 



1'he preepisternai)!. In some of the more 

 generalized insects there is a sclerite situated 

 in front of the episternum; this is the pre- 

 episternuwi (Fig. 61, Peps). 



The paraptera. In many insects there is on 

 each side a small sclerite between the uppjr 

 end of the episternum and t lie base of the wing; 

 these have long been known as the paraptera. 



Fig 62. Lateral aspect Snodgrass (TO a) has shown that there are in 

 oi the meso- and meta- 

 thorax of Mantispa some insects two selerites in this region, which, 



rugicolhs; i i anepis- ^ designates the cpistcnial paraptera or 

 ternum; 2, 2, katepister- 

 num; 3, ?, anepimer- preparaptera (Fig. 61, iP and 2P>, and that 



one or occasionally two are similarly situa' 

 between the epimerun and the base of the wing, 

 the epimeral paraptera or post paraptera (Fig. 61, $P and //' 



