HEMIPTERA. 171 



The Pear-tree Psylla, Psylla pyri. — This is a minute species which 

 measures only 2.5 mm. (o. 1 inch) to the tip of the folded wings. It 

 invests the smaller limbs and twigs of pear-trees, causing them to 

 droop and fall off. It can be destroyed in the same way as recom- 

 mended for plant-lice in the same situation. 



Family VI. — MEMBRACID^E.* 



{Trcc-hoppcrs.) 



We have many common representatives of this sub-family; and 

 the grotesque forms of certain species are sure to attract the attention 

 of collectors. The general outline of the body is usually triquetral, 

 that is, shaped like a beech-nut. But many of the species have one 

 or more of the angles prolonged, or are furnished with prominent 

 humps or tubercles. The most useful character for distinguishing 

 members of this family is the prolongation of the prothorax back- 

 ward above the abdomen. Sometimes it extends back to the tip of 

 the abdomen, and completely covers the wings. This development 

 of the prothorax reminds us of what occurs in the Tettiginae, of the 

 order Orthoptera. 



Many species of the Membracidae live upon bushes or small trees ; 

 and all are good leapers. Hence the common name, Tree-hoppers. 

 Although these insects subsist upon the juices of plants, I have never 

 known them to occur in sufficient numbers to be of economic impor- 

 tance. Some members of this family excrete honey-dew, and are at- 

 tended by ants, as are the Aphids. The transformations of but few 

 species have been observed. Some of these make slits in twigs, in 

 which they lay their eggs. The immature forms of certain species oc- 

 cur upon plants in company with the adults. But the early stages 

 of the great majority of species are unknown to us. 



The genus Darnis will serve as a good illustration of one of the 

 principal types of this family. Here the prothorax is nearly 

 all that can be seen of the body from above. It is very convex 

 in front, overshadowing the short, transverse, band-like head, 

 and tapers to a sharp point, which extends beyond the tip 

 of the abdomen. (Fig. 140.) 



The Buffalo Tree-hoppers, Ccrcsa bilbalus, represents 

 another type belonging to this family. The popular name refers to 

 the lateral prolongations of the prothorax, which suggest the horns 



* Membracidae, Membracis : membrax {nditfipaZ,), a kind of Cicada. 



