THE EXTERNAL ANATOMY OF INSECTS 



51 



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

 thorax is divided into two parts by the prescutum; these separated 

 halves of the scutum are called the parapsides (see Fig. 1 130A). 



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

 the sclerites of the left pleunim 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 anepister- 

 num and the katepisternum respectively (Fig. 62). 



The epimerum. — The epimerum is the more posterior of the two 

 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, Wp) 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 upper and a 

 lower part. These two parts have been desig- 

 nated by Crampton ('09) as the anepimerum 

 and the katepimeruni respectively (Fig. 62). 



The preepisternum. — In some of the more 

 generalized insects there is a sclerite situated 

 in front of the episternum; this is the pre- 

 episternum. 



The paraptera. — In many insects there is on 

 each side a small sclerite between the upper 

 end of the episternum and the base of the wing ; 

 these have long been known as the paraptera. 

 Snodgrass (10 o) has shown that there are in 

 some insects two sclerites in this region, which, 

 he designates the episternal paraptera. or 

 preparaptera (Fig. 61, iP and 2P); and that 

 one or occasionally two are similarly situated 

 between the epimerum and the base of the wing, 

 the epimeral paraptera or postparaptera (Fig. 61, 3P). 



Fig. 62. — Lateral aspect 

 of the meso- and meta- 

 thorax of Mantis pa 

 rugicollis; i, i, anepis- 

 ternum ;2, 2, katepister- 

 num; 3,3, anepimer- 

 um; 4,4,katepimerum; 

 c, c, coxa. 



