16 BULLETIN 85, UNITED STATES NATIONAL MUSEUM. 



but the urite is well developed. The tenth segment is represented 

 by the ventral genital valve, bearing the forceps on its upper margin. 

 The eleventh segment is the anal valve, the dorsal sclerite bearing 

 the anal opening at its extremity. The term supra-anal plate applied 

 by some to tliis sclerite is hardly correct, for it is not above the anus, 

 as the term implies, but bears the anus; hence the term anal valve. 



The spiracles are quite dependable for the interpretation of the 

 abdominal segments, and it seems" obvious that the above statements 

 are correct. However, the best and surest method of determining 

 the actual number of the segments is by embriological studies. Until 

 such studies are made the conclusions can not be absolutely certain. 



LOCOMOTION. 



The Psyllids are usually very active little creatures and often 

 difficult to catch without the aid of a net. The rapid movement is 

 a combination of leaping and flying. When disturbed a psyllid 

 throws itself into the air by means of its powerful hind legs, and 

 once in the air it vibrates its wings and thus increases the rapidity 

 of movement and the distance covered. The wings are scarcely 

 strong enough to permit of rapid or prolonged flight unaided by the 

 preliminary leap. By this combined leaping and flying, however, 

 the insect is able to travel several yards, although more often it 

 merely leaps a few inches or feet from the point of disturbance. 



The hind legs are much larger and longer and more muscular than 

 the others. The femur is directed backward, the tibia bends forward 

 and the tarsi backward. For leaping, the insect doubles the tibiae 

 close up under the femora and the tarsi close under the tibiae, and 

 fastened firmly by means of the claws. The tarsi are so short that 

 the claws are nearly under the trochanter, when the leg is doubled for 

 leaping. By suddenly extending the tibiae by means of the powerful 

 muscles in the femora and coxae the body is thrown upward and 

 foi-ward. This may be most easily understood if one folds a piece 

 of paper in the form of a Z with the base short, and performs the 

 motions described above. 



RELATIONS TO OTHER HOMOPTERA. 



It seems apparent from the morphological studies on tliis family 

 that it is less closely related to the Aphididae, Aleyrodidae, and Coc- 

 cidae than has been heretofore supposed. Many things point to a 

 close relationship with the higher Homoptera, especially the Cica- 

 doidea, and the Membracidae, and related families. The writer is 

 not yet prepared to make any definite statement in this regard. It 

 is to be hoped that more work will be done in the future with a view 

 to establishing the true relationships between the families of Homop- 

 tera. The sclerites of the head and thorax, the number of abdominal 

 segments present and suppressed, many features of the internal 



