20 



hibernating generation feed and breed on the lower or earlier-appear- 

 ing leaves, gradually disappearing as the season progresses, but not 

 before some of their progeny have reached the adult condition. Some 

 weeks are spent by the adults in the spring in feeding before egg- 

 laying begins. Eggs are placed just beneath the epidermis in the 

 lower leaf surface, usually singly but also in groups of from 6 to 9, the 

 egg stage, according to Professor Slingerland, lasting from 9 to 14 

 days. Egg-laying probably continues for two months or more. 

 When just hatched the young hopper is very small, whitish in color, 

 with red eyes, later becoming striped with j^ellow. In the course 

 of their growth these nymphs molt four times, the white skins being 

 very numerous on the lower surfaces of badly infested leaves, as 

 shown in figure 6, at g. The nymphs feed in the same manner 

 as the parents, sucking juices from the leaves, at first on the lower 

 surface of the older leaves where they were born, but later spread- 

 ing more or less generally over the plant. They are very agile, 



Fig. 6.— Grape leaf-hopper ( Typhlocyba comes): a. Adult female; b, adult male; c, another form of 

 the species, showing variation in markings; d, newly-hatched nymph; e, last stage nymph; /, 

 appearance of injured leaf; ^, cast pupa skins, a-f , Much enlarged; ^, less enlarged; /, reduced. 

 (From Marlatt.) 



running in all directions, but do not leap or hop. In New York State 

 Professor Slingerland found that from 30 to 35 days were required 

 for their development in summer to the adult, and that there is but 

 one full generation and a partial second brood of nymphs each year, 

 the individuals of this partial second brood probably not maturing 

 before frost. In warmer parts of the country two full generations or 

 more are probable, since Gillette has shown this to be the case for 

 Colorado and Townsend for New Mexico. By late summer the 

 insects are often exceedingly abundant, and all stages are to be found 

 on the leaves. The continued effect of their feeding is very apparent, 

 the leaves being yellow and brown-blotched, the older ones most 

 affected (figure 6,/). Feeding continues until the approach of cool 

 weather, when the "hoppers" seek suitable hibernation quarters, as 

 stated. 



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