208 INTERNATIONAL CONGRESS OP VITICULTURE 



hatched larvae do not have the strength to move far before first partaking 

 of food and if this is not nearby they perish. 



Hatching. This occurs during the entire month of June and early July 

 being most active from about June 10th to July 1st. A very early season may 

 cause a few to hatch the last week of May. 



Feeding habits of the larvae. These grubs seek the green tissues either 

 of the shoots or of the foliage but principally the upper surfaces of the 

 latter, although some feeding occurs on the under surface of the leaves also. 

 They are often found devouring the young flower buds and also feed on the 

 blossoms. The extent of injury caused by the larvae is small aHhough we 

 have seen a few vines which had the leaves badly eaten by them. Our 

 object in killing the larvae is to destroy the developing crop of beetles which 

 would injure the crop the following season. 



Summary of Life History. 



There is only one generation of beetles annually although the genera- 

 tions of two years overlap. The length of life of the insect, counting the 

 egg stage as a part, is slightly more than 13 months. During the latter part 

 of June it is sometimes possible to find all four stages of the insect, but 

 usually all the eggs have hatched before any of the larvae have entered the 

 pupal stage. The egg stage averages about one month in duration, the larval 

 period is slightly over three weeks, the pupae require about two weeks before 

 emerging as beetles, and since the adults emerge about the last week in July 

 and live until the middle of June their life is about 11 months. These are 

 averages and for the Lake Erie Valley, but even here it is possible for the 

 maximum length of life to be 15 months. 



Natural Control. 



The grapevine flea-beetle fluctuates in numbers considerably from one 

 season to another, but the exact causes of these variations have not been 

 determined. The eggs are not attacked by parasites to any extent. The 

 larvae, however, are preyed upon by a species of carabid which closely re- 

 sembles the adult flea-beetle in size and color. 



These insects were not found in numbers so their activity does not de- 

 crease the number of larvae to any great extent. The writer has found the 

 nymphs of one of the Pentotomidae piercing the bodies of the larvae and 

 sucking the body fluids. Unfortunately the few nymphs found died before 

 reaching maturity thus preventing the determination of the exact species. 

 From the account given by Slingerland,6 we surmise that these were the 



In the vineyards the adults do not appear to be fed upon by birds but we 

 do not know to what extent this takes place in late summer. We have not 

 been able to estimate the number of beetles that are destroyed by climatic 

 factors and predaceous enemies after leaving the vineyards. This is due to 

 the scattering of the beetles over large areas where their observations is 

 most difficult but it appears that the greatest reduction occurs during the 

 period of adult life. 



6 Slingerland, M. V. Cornell Agr. Expt, Sta. Bui. 157, pp. 203, 204. 

 nymphs of Podisus modestus, Dallas. This author also reports finding a 

 common lady beetle, Megilla maculata, De Geer, feeding on the young grubs. 



