stough: the hackberry psylla. 127 



5, y), forming the attachment for a membrane which runs 

 caudad between the front coxae, and which will be mentioned 

 more fully later. The outline of the compound eye is somewhat 

 more angular than rounded, viewed from either the front or 

 the rear. 



In my study of the sclerites of the head I have followed Com- 

 stock and Kochi, and my conclusions for Pachypsylla agree 

 largely with the facts recorded by them. 



ANTENNA. 



The antennae are filiform, rather stout (a characteristic of 

 the genus Pachypsylla), and average 0.83 mm. long. They are 

 10-segmented (28-S). The relative lengths of the ten an- 

 tennal segments on the basis of the length of the first segment 

 may be represented thus: 1, 1, 2, 1.2, 1.1, 1.2, 0.8, 1, 0.7, 0.4; 

 the second segment is wider distally than proximally and is 

 distally notched; the fourth, fifth, sixth, seventh and eighth 

 segments are constricted proximally ; the tenth segment is the 

 smallest segment and bears at its distal end two stout, blunt, 

 diverging spines (fig. 12) , which are about as long as the seg- 

 ment and appear to be hollow. The last few segments are 

 compressed dorsally. 



The cuticula of the first two segments is very deeply rugose, 

 forming scales, which on the second segment become longer 

 at the distal end (28-S). The surface of the remaining seg- 

 ments is covered with deep, transverse corrugations (28-Q) , 

 'which give to each segment a sharply serrate lateral edge, the 

 teeth pointing distad. A fringe of sensory hairs is found on the 

 distal ends of the segments, and a few scattered along their 

 surfaces, the tenth segment being without conspicuous hairs. 

 Figure 9, plate XXXIV, shows the last four segments, with 

 their corrugations and the terminal spines, while figure 6, 

 plate XXVIII, is of the articulation of the third and fourth 

 segment, showing the sensory hairs and the cuticular struc- 

 ture. 



MOUTH PARTS. 



The suctorial mouth as found in the homoptera, and as de- 

 scribed by Meek (1903) and others, consists of labrum, epi- 

 pharynx, labium, hypopharynx, and setae. These parts are all 

 represented in Pachypsylla. Closely associated with them are 

 the frons, clypeus, mandibular and maxillary sclerites, and 

 tentorium, corresponding in position to those in the cicada. 



