419 



mesothorax and an approximation of the epimera on the ventro-meson 

 in the metathorax; all of which is accompanied by an enormous de- 

 velopment of muscles within the thorax in preparation for the active 

 life of the adult. The wing-cases, too, are early approximated, and 

 there is a corresponding reduction in the size of the mesonotum and 

 metanotum. 



Mesonotwn. — The mesonotum is divided into two regions by the 

 closing together of the mesepisterna. The cephalic one, the prescutum, 

 just caudad of the pronotum, is a shield-shaped plate with slightly 

 projecting cephalo-Iateral angles. On the cephalic margin of this piece 

 on the meson there is an invagination, the prephragma, which, how- 

 ever, is usually not well developed in the nymph. The second portion 

 of the mesoscutum lies between the cephalic pair of wing-cases. This 

 represents combined scutum, scutellum, and postscutellum. It is nar- 

 rowed cephalad, has a sliglit projection on each cephalo-Iateral angle, 

 the anterior wing-processes (Fig. 21, awp), and a similar, longer, one 

 on each caudo-lateral angle, the posterior wing-processes (Fig. 21, 

 pwp). Near the cephalic margin on the meson is an invagination indi- 

 cating the location of the mesophragma. Immediately caudad of the 

 mesoscutum and between the second pair of wing-cases is the 

 metascutum. This is similar in shape to the caudal sclerite of the 

 mesoscutum, though somewhat larger, and possesses similar wing- 

 processes on its lateral angles. There is no subdivision of the 

 metascutum, but there is a deep invagination on the meson near the 

 cephalic margin— the metaphragma. 



Mcsothoracic Spiracles. — These are located just laterad of the 

 prescutum and are always hidden to a greater or less extent by the 

 overlapping pronotum. Large tracheae are connected with them and 

 the spiracles are doubtless functional during nymphal life. The meso- 

 stigmal plates are wanting in the nymph, and their derivation will be 

 discussed later, in the description of the adult. 



Mesopleura. — These sclerites, occupying somewhat more than the 

 cephalic half of the lateral aspects of the pleura, are approximate on 

 their dorsal margin between the prescutum and the wing-cases. The 

 dorsal border extends from the mesostigma caudad to the second pair 

 of wing-cases. The cephalic margin follows the'caudal margin of the 

 pronotum and extends ventrad from the mesostigma to the mesocoxae. 

 The ventral border follows the contour of the coxal cavity; and the 

 caudal border, forming a suture which may be known as the inter- 

 pleural suture (Fig. 25, insu), extends from between the mesocoxae 

 and metacoxae dorso-caudad to near the base of the second pair of 

 wings. The mesopleura are each divided by three furrows into three 



