190 APPLIED ENTOMOLOGY 



during late July and August. Most of these species are somewhat larger 

 than the Periodical Cicada and generally black and olive-green, with a 

 white powder or " bloom" on the under side of the body. They are 

 supposed to have about a 2-year life history and as individuals occur 

 every year, two distinct broods. A few of these species greatly resemble 

 the Seventeen-year Cicada in. col or but are smaller, and as they appear 

 more than a month after the latter have disappeared, no confusion should 

 lead to the belief that the Seventeen-year Cicada has appeared at that 

 season. 



FIG. 179. FIG. 180. 



FIG. 179. Adult Dog-day Cicada (Tibicen linnei Sm. and Grsb.), natural size. 

 (Original.) 



FIG. 180. Tree-hoppers showing remarkable forms of the pronotum. Enlarged 

 about twice. (Original.) 



Leafhoppers and Treehoppers. The four or more families included 

 under this heading contain a large number of kinds of insects, many of 

 which are extremely numerous. Among them are the lantern-flies of South 

 America and the candle-flies of China and India which are quite large insects, 

 a number of which at least are luminous. Some of the insects here in- 

 cluded are highly colored and some secrete quantities of wax which is often 

 used for candles and other purposes. 



In one of the families the Treehoppers the pronotum is largely and often 

 remarkably developed, sometimes giving these insects a very grotesque appear- 

 ance. In this country, however, such forms are not usual, the development of 

 this section of the body being mainly in the line of horns or humps and the 

 enlargement of this plate in width or height and in its extension backward until it 

 covers most or all of the body (Fig. 180). The Treehoppers of the United States 

 are all small insects, less than half an inch long, and as they sit on twigs their 

 peculiar forms seem to give them resemblances to buds, swellings or other charac- 

 ters, which suggests that their odd outlines may be for resemblance to these 

 structures and thus secure the protection from their enemies which this would 

 give. 



In general the Treehoppers puncture the twigs of plants and are injurious, 

 though only a few kinds are ever so abundant and attack plants of such impor- 

 tance as to need consideration. 



Among these the most common is the Buffalo Treehopper (Ceresa bubalus 

 Fab., Fig. 181) found practically everywhere in the United States except perhaps 



