STOUGH: THE HACKBERRY PSYLLA. 161 



with several small sclerites at their bases embedded in the 

 membrane. These are illustrated in figure 79, which shows 

 the tendons controlling their movement, and the two-lobed 

 empodium, one lobe being under each claw. This empodium 

 is functional, as in many insects, and is used in holding the in- 

 sect to a smooth surface, as it can cling readily to a glass sur- 

 face. 



Femora, tibise and tarsi of all three pairs of legs are cov- 

 ered with hairs, many of which are probably tactile. Both 

 coxae and trochanters (except of metathoracic legs) bear hairs, 

 the latter with one or two hairs on their distal ends longer 

 than the segments themselves. On the trochanters is a row 

 of oval sensory pits (fig. 77, sp) . 



ABDOMEN. 



The relative shapes of the abdomen in the sexes can be 

 seen in 35-lS and 14 (figure inverted), also in 5^-4. The 

 abdomen of the female is larger than that of the male and 

 seems much longer in proportion, as the ninth segment of the 

 male bearing the genitalia is generally carried bent dorsad 

 and cephalad so that the supra-anal plate fits up tightly against 

 the seventh segment, thus making the abdomen appear quite 

 short. In both sexes it is slightly compressed laterally. Ac- 

 cording to Edwards, there are visible five segments above and 

 six below, not counting the genital segment. 



The first two segments are smaller than those caudad. "The 

 first abdominal somite of both sexes is added to the meta- 

 thorax to enlarge the springing-gear ; the second abdominal 

 somite forms a short stalk for the abdomen. . . ." — 

 (Macloskie.) 



According to Witlaczil, in the male the supra-anal plate rep- 

 resents the tenth somite, the ninth is not represented above, 

 and below forms the subgenital plate; the eighth is scarcely 

 at all developed above ; in the female, the supra-anal and sub- 

 genital plates or valves represent the tenth segment. 



In the pleural membrane are found seven spiracles, each 

 surrounded by a wide, chitinized ring. The cuticula of the 

 abdomen is punctate, not so pubescent as that of the thorax, 

 and the membrane between the chitinized plates of each seg- 

 ment is covered with great numbers of minute sensiUia stylo- 

 conica. On the posterior edge of each segment is a row of 



a-Univ. Sci. BulL. VoL V, No. 9. 



