142 TRANSACTIONS OF THE ILLINOIS 



the hind wings are quite slender. The abdomen of the females is termi- 

 nated by a conical ovipositor, and in the males is usually furnished with 

 several short erect appendages; but in neither do we find the cornicuH or 

 honey tubes, so common in the true Aphides. The tursi, as before stated, 

 are two-jointed; and all the species possess the power of leaping, like the 

 leaf-hoppers, hence the generic name Psylla (which formerly included all 

 these species), which was the Greek name for a jumping insect, was given 

 to them by Geoffroy. Their general habits are very similar to the leaf- 

 hoppers, with which, in this respect, they appear to be closely allied. 



They subsist, in all their stages, upon plants ; and the species are 

 doubtless very numerous, although but few, as before stated, have been 

 described in this country. The larvae have the body quite flat, the head 

 broad, the abdomen rounded, and the antennae, at first, apparently one- 

 jointed ; the pupae show the rudimentary wings in the form of four 

 comparatively large, broad scales, attached to the sides of the thorax. 

 Many of the species are covered, during the larva state, with a delicate 

 cottony substance, usually arranged in flakes; though some, as our most 

 common species, are naked. A few species, as for example one which 

 inhabits the hackberry, form galls, in which they reside. 



The species, so far as 1 am aware, without any exceptions, deposit 

 eggs, from which the young are hatched, and do not bring forth living 

 young as do most of the true Aphides. 



The characters, therefore, by which we may distinguish them from 

 the Aphides, are as follows: 



The two little bristles at the tips of the antennae ; . their habit of 

 leaping ; the form of the head, and the veining of the wings. 



The family has been divided into quite a number of genera, some of 

 which depend on very slender characters, but at present we shall have 

 occasion to refer only to two or three of these. 



Genus Diraphia. 



There are no common names by which to distinguish this or other 

 generic groups from each other. I am unable to give, at present, the full 

 characters of this genus, which, I believe, was established by Mr. Waga; 

 but as it was originally included in Livia, with which it is closely allied, 

 I may, from this fact and from the characters of some of the species, 

 give sufficient for the reader to locate species with reasonable certainty. 



In Livia the head is square, flat above, deeply cleft in front, extend- 

 ing anteriorly in two conical tubercles; no ocelli, or little eyes; antennae 

 not much longer than the head and thorax; ten-jointed, the first joint 

 short and thick, the second joint much dilated or enlarged, and three or 

 four times as long as the first; the seven following of equal size, small, 

 tipped at the end with two minute bristles, usually of unequal length; 

 wings as heretofore described, except that the front pair are sometimes 

 slightly leathery and but semi-transparent. 



Serville and Amyot say that Diraphia differs from this only in having 

 the head much larger, and in the second joint of the antennae not being 

 comparatively as long as in that genus. They also appear to doubt the 



