THE JUMPING PLANT-LICE OR PSYLLIDiE OF THE NEW WORLD. 9 



Aphalara (fig. 166) or it may be uniform to the margin and the suture 

 between it and the pleurites indistinct. 



The pleurites, in most genera, are easily visible, but in Livia they 

 are less so (fig. 3). The pleural suture is distinct, extending from 

 the base of the forecoxse to the lateral extremity of the pronotum. 

 The episternum may be equal in size to the epimeron, or it may be 

 larger, but it is seldom smaller. A small trochantin is usually visible 

 at the lower end of the episternum. 



The taxonomic value of the form of the pleurites of the prothorax 

 has been emphasized elsewhere in this paper. In some genera, as 

 in Aphalara (figs. 1, 166), the pleural suture extends to the middle 

 of the knoblike lateral extremity of the pronotum, while in others, 

 as in Psylla (figs. 4, 8), it is oblique and extends to the posterior edge 

 of the lateral extremity of the pronotum, and the latter is not knob- 

 like. The episternum is often more or less covered by the receding 

 eye and occiput (Euphjllura, fig. 35), or both pleurites may be so 

 covered. The epimeron often is partially concealed by the con- 

 junctival membrane between the pro- and mesothorax. 



The prosternum is greatly reduced in most genera, the forecoxge 

 being contiguous and occupying most of the space. In Apsylla, 

 however, the prosternum is much larger and the forecoxse are not 

 contiguous (fig. 9). In fact, the condition in this genus in this regard 

 resembles very much the nymph of the more specialized genera. In 

 the latter genera the furcse of the prosternum are strongly developed, 

 as pointed out in connection with the labium. The attachment of 

 the furcse on the sternum is not strongly chitinized, but a short 

 distance from the base they become very thick and strong, forking 

 about midway from base to apex. The apical arms are very heavy 

 and knobbed at the end and roughened. Several very large muscles 

 are attached here. 



Between the pro- and mesothorax are three small chitinized sclerites 

 which are not visible on a dried specimen unless it be distended by 

 means of a warm liquid. One of these is the peritreme bearing the 

 mesothoracic spiracle and is, therefore, not part of the prothorax. 

 Lying close to the upper margin of the peritreme and sometimes not 

 separated from it is a second sclerite which is sometimes small and 

 elliptical and extends only a little above the upper edge of the pro- 

 pleurites, and sometimes long and narrow and extends far up between 

 pro- and mesonotum. In Apsylla these two sclerites are one (fig. 2), 

 while in Trioza alhifrons (fig. 7) they are divided only by a line. In 

 other species they have become more or less separated, but it seems 

 obvious from the two species mentioned above that the upper sclerite 

 is only a part of the peritreme, which has become separated for some 

 reason from the lower part. Stough called this upper sclerite the 



