198 INTERNATIONAL CONGRESS OP VITICULTURE 



True one can find individuals on grapes on all soils but not in the same 

 amount as on the lighter soils. 



Description. 



Eggs. The eggs are partially transparent, slightly curved or bean 

 shaped and are between .7 mm and .8 mm (about .03 inch) in length and 

 from .2 mm to .3 mm (about .01) in diameter. 



Nymph. The young leaf-hoppers resemble the adults in general shape 

 but lack wings. In the place of the latter we find thickened areas which 

 are the developing wings, also called wing pads. These increase in size 

 with each moult disproportionately to the other parts of the body. These 

 nympths are yellowish-white in color with red eyes during the first instar. 

 They pass through five stages or instars and at the last moult upon chang- 

 ing to adults the wings unfold. The eyes change to yellow in the second 

 instar. 



Adult. The adult insects have a general color of yellow and are vari- 

 ously marked with darker yellow or salmon irregular areas. Several black 

 spots are found on the wings. The variation in color and shape of the 

 colored areas and spots is so great that nine species have been described 

 but these are now regarded as varieties of Typhlocyba comes. The black 

 spots remain constant but the irregular areas change in color from yellow 

 to salmon while individuals having areas of light red have been found. 

 These variations in color vary with the season. The typical color during 

 early summer while the insects are feeding on grape foliage is yellow, but 

 during late summer and autumn they change to a salmon and often to a 

 red. This darker phase is found in the those hibernating and also while 

 they are feeding in the spring, but as soon as feeding is resumed on the 

 grape the color changes to a light yellow. The typical comes is the com- 

 mon variety on Concord vines in Chautauqua County, New York. Although 

 a number of the variety octonotata are also found. 



Seasonal History. 



The eggs hatch during the latter part of June and July of a normal 

 season although they have been observed hatching during early August. 

 The nymphs feed by sucking the sap from the leaf, practically all feeding 

 being done on the underside. They require from three to five weeks to 

 reach maturity depending upon temperature. The majority of these nymphs 

 change to adults from July 10th to July 25th of a normal year but nymphs 

 of the first brood are often found during early August. If weather condi- 

 tions are such that a second brood is not produced, the adults appearing 

 in July and August continue to feed on the grape foliage until the fruit 

 is harvested and the leaves begin to fall. We then find them dispersing 

 to other food plants but especially to locations where rubbish and leaves 

 have been collected by the wind and where they remain during the winter. 

 They are active on the warm days of autumn but during cooler weather 

 remain quiet in their shelter. With the warm spring days we find them 

 resuming feeding on the plants previously mentioned. The adults mate 

 during May and early June. The males die before the females, few of the 



