224 NATURAL HISTORY OF ARTHROPODS. 



protracted forwards. Each side of these the filiform, ten-jointed antennae, are situated, 

 and these are thick at base, but armed at tip with two slender bristles, or less com- 

 monly with one. The rostrum is short, three-jointed, and placed almost between the 

 fore-coxre, where it fits into a grooved space. Both sexes are always winged in the 

 adult, the wing-covers are ample, and while often transparent, are much thicker than 

 the wings, and furnished with stout curving veins, which enclose a few areoles at tip. 



This group is divided into three prominent sub-families, the Liviina, the Aphalarina, 

 and the Psyllina. 



The first may be recognized by the long, flat, chisel-shaped head, with narrow eyes, 

 and antennas with one bristle at tip ; the second by the frontal lobes not being 

 detached from the vertex, besides the lengthened cubital petiole of the fore-wings, 

 which is as long or longer than the discoidal part of the subcosta ; and the third by 

 the prpminent round eyes, detached frontal lobes, and short petiole of the cubitus. 



Many exquisitely decorated little insects adorn this group, but the giant and chief 

 of all, though not so prett}', is the neat Pacliypsylla venusta, which inhabits the Celtis, 

 or Hackberry, in the United States. This fine species expands nearly half an inch 

 across the open wing-covers, is of a grayish clay color areated with brown, and has a 

 double oblique row of squarish, dark brown spots along the posterior margin of the 

 wing-covers. By arresting the flow of sap in the petiole of Celtis, it produces a round 

 gall which steadily increases in size until it becomes as large as a filbert. This, when 

 dry and hanging upon the stalk in autumn or winter, is so coarse and hard as to 

 resemble the shell of a rough pignut. 



Other species of smaller size, such as the Pachypsylla celtidis-mamma and allies, 

 make button or cabbage-shaped galls upon the leaves of Celtis, and which also become 

 hard and dry by the time of leaf-fall in autumn. 



The Psylla tripunctata is a wax-colored species with three brown curved streaks, 

 and three darker dots near the posterior margin of the wing-covers. It is peculiar in 

 living upon the leaves of blackberry, which it causes to wrinkle and purse, white it is 

 equally common among the needles of pine trees. 



Calophya mgripi?mis is a smaller black species wdth orange thorax, which lives upon 

 the stems and leaves of sumach, and appears fully developed in June and July. The 

 larvse, resembling rough grains of gunpowder, may be seen spread over the twigs of 

 that bush throughout the winter and spring. After the wing-flaps have developed 

 late in spring, the nymph has the form of a very broad trilobite, and sticks close to the 

 bark like a scale-louse. 



A more lengthened and depressed form apj)ears in the genera Livia and JDiraphia, 

 both of which are common upon Calamus and reeds in swampy places of the Atlantic 

 region, although the former is often abundant upon pines and the sugar-maple. 



In the family Membracid^ we meet with typical Homoptera having three-jointed 

 tarsi, and composing a numerous assemblage of the most grotesque and extraordinary 

 forms of this order. It is, however, chiefly in the prothorax that these curious modifi- 

 cations prevail, and when this is stripped off, as indeed occurs naturally in some spe- 

 cies of Centrotus, we observe forms which have a body much like the Psyllidae, but 

 with broader vertical heads set beneath the thorax, and with two ocelli on the face. 



They are of every conceivable form, arched, compressed, depressed, hump-backed, 

 spindle-shaped, pointed at both ends, inflated, hemispherical, conical, and so forth, and 

 are furnished with an equal variety of superficial attachments. The antennaj are short, 

 bristle-shaped, thick at base, and situated under the expanded margin of the clypeus. 



