236 Annals Entomological Society of America [Vol. XI, 



plate. In the epimeron a similar cleft is found, but this is 

 nearly surrounded by chitin and does not open broadly as does 

 that of the episternum. The sternum, save a small anterior 

 plate and a piece between and behind the coxae, is almost 

 entirely membranous. 



In the Cercopidse (Figure 6) there occurs in the lower 

 epimeron, partty covering the meron of the coxa, a flap-like 

 process, which may be the homologue of a similar process on 

 the lower epimeron of Fulgoridas (Figure 9). 



Also meriting particular mention are the pleuron, sternum 

 and coxa of the Psyllid metathorax (Figures 10 and 11). In 

 the generalized forms, Apsylla (Figure 10) for example, the 

 pleuron and coxa are not radically different from those of 

 other Homoptera, but in certain higher forms like Arytaina 

 rohusta (Figure 11) some remarkable conditions obtain. The 

 pleuron, particularly the epimeron (em), is greatly reduced, 

 w^hile the coxa (ex) has become enormous. The pleural suture 

 (p) no longer extends from the wing articulation to the coxal 

 condyle, but seems to end arbitrarily on the lower margin of 

 the pleuron. The coxal articulation (x) occurs at the center of 

 the lower margin of the greatly reduced epimeron (em). The 

 pleuron and coxa thus present the appearance of the latter hav- 

 ing become extended far up the side of the body, replacing the 

 former to a great extent. In this shifting the coxa seems to 

 have carried with it along the lower margin of the pleuron its 

 articulatory process (x), which in other forms, is almost univer- 

 sally found at the end of the pleural suture. In the Psyllids 

 there is no distinct precoxale in the metathorax, but the narrow 

 postcoxale (poc) is remarkably long and distinct. It is possible 

 that the large trochantin (tns) figured by Crawford, 1914, may 

 be a region homologous with the precoxale found in other 

 forms. The coxa bears on its lower posterior side an articulated 

 meracanthus (mc). 



In the metathorax of Aleyrodidas (Figure 13) the pleural 

 suture (p) is only partly distinct, the upper part being wanting. 

 A continuation of the pleural suture extends the entire length 

 of the coxa, which is apparently fused with the pleuron. 



Sternum. The sternum of Psyllidas is represented by a very 

 narrow sclerite between the coxae, hardly visible from the side. 

 Aside from this and the modifications noted above in the 

 Fulgoridae, the metathoracic sternum is fairly normal. 



