THE JUMPING PLANT-LICE OR PSYLLID^ OP THE NEW WORLD. 11 



process, with the axillary cord usually fused with it and forming 

 part of the attachment base for the anal angle of the wing. 



The 'pleural suture is distinct from the coxa to about the middle 

 of the pleura, but from the wing process downward to this point it 

 is usually either obsolete or very indistinct. In ApsyTla, however, 

 and also Livia and Euphyllura and perhaps other genera the suture 

 may be traced to the base of the wing process, its course being rather 

 tortuous. A little above the coxae may be seen the lateral apodemes 

 of the mesopleurse, as invaginations on the pleural sutiu-e. The 

 lower end of this suture is at the articulatory condyle of the mesocoxa 

 and usually meets the margin of the episternum at the same point. 



The episternum is somewhat larger than the epimeron and has a 

 long line of articulation with the mesosternum in front of the coxa. 

 The epimeron articulates above with the postscutellum and also with 

 the scutum and below with the coxa. Below the wing base in many 

 species is a more thinly chitinized and impressed area of irregular 

 outline. 



The mesosternum also is very large and extensive, forming even 

 more of the sternum relatively than the mesonotum does of the entire 

 thoracic dorsum. It extends for^vard to the forecoxae and is flexed 

 upward at tliis point with the anterior margin arcuate inward to 

 allow for the labium which passes out behind the forecoxae. From 

 near the posterior margin, between the mesocoxae, arise the meso- 

 furcae. These are a little larger than the profurcae, and the end of 

 each arm is broadened out T-shaped to facilitate muscle attachment. 

 A narrow prolongation of the sternum extends back between the 

 coxae, but not beyond this point. 



Metathorax. — The metathorax presents more remarkable develop- 

 ments and speciahzations than any other part of the body. This 

 is especially true of the pleurae and the endoskeleton and has been 

 caused by the habit of leaping wliich has necessitated unusually 

 strong attachments for the relatively gigantic muscles found in the 

 thorax of these insects. 



The metanotum is much smaller and less conspicuous than the 

 mesonotum. The praescutum of the metanotum is almost or com- 

 pletely suppressed. The scutum forms the largest part of the 

 notum and articulates with the wing process of the hind wings. 

 The scutellum is similar in shape and appearance to the mesoscu- 

 tellum, but is usually smaller. An axillary cord extends down 

 from it to the wing process, as in the mesothorax, and forms the point 

 of attachment for the anal angle of the hind wing. 



The postscutellum, or pseudonotum, is much larger than that of 

 the mesothorax, and is very often produced into a pair of horn-like 

 processes or very prominent ridges. It extends down laterad and 

 articulates with the epimeron. 



