20 BULLETIN 901, U. S. DEPARTMENT OF AGRICULTURE. 



The maximum limits of records of individuals transforming in the 

 ground were from July 7 to August 29. The duration of this period 

 of transformation averaged 16.15 days in 1916 and 14.50 days in 1917, 

 or about 5 days less in each season than those required for the "large 

 form." The average duration of the different stages in the ground 

 was as follows: Prepupa 4.68 days, pupa 7.24 days, callow adult 

 2.19 days. 



After emergence from the ground the beetles feed until late in 

 autumn and then go into hibernation. A comparison of the fore- 

 going with the seasonal history of the typical grapevine flea-beetle 

 shows that the lesser species appears in the vineyard about three 

 weeks later than the other and continues later throughout the season. 

 The typical species disappeared from vineyards at the season indi- 

 cated by Slingerland (19), while the "small form" was present at the 

 time that the "tardy individual," referred to by him, was found 

 ovipositing, some time after the overwintering adults of the typical 

 species had disappeared. Following Slingerland's suggestion a little 

 further, it seems probable to the writer that the collection of beetles 

 of the "small form," if confused with the typical species, could easily 

 give rise to the two-brood hypothesis. 



This comparison also shows that the lesser grapevine flea-beetle 

 is more rapid in its development, particularly in the larval and 

 prepupal stages. This more rapid development can not be attributed 

 to any extent to the fact that the larva? appear later in the season, 

 for even late individuals of the "large form" reared at the same time 

 as the early individuals of the ' ' small form ' ' required more time for 

 their metamorphosis. 



ECONOMIC IMPORTANCE. 



The grapevine flea-beetle, according to all accounts, has been one 

 of the most destructive of insects to the grape industry. Slingerland 

 (19) wrote in 1898 that for several years previous it had done more 

 damage to vineyards in New York than all other grape insects com- 

 bined. Emerging from hibernation at the time when the grape buds 

 are swelling, a single beetle, by eating out comparatively few buds, 

 destroys as many shoots and a much larger number of clusters. If 

 the injury is repeated, according to Quaintance and Shear (22), the 

 vines themselves may be weakened or killed. Feeding after the 

 grapes come into leaf, either by the adults or by the larvae, is less 

 destructive. 



Compared with its larger relative, the lesser grapevine flea-beetle 

 is greatly limited in its possibilities for destructiveness, because the 

 adult does not emerge from hibernation early enough to attack the 

 buds, but, like the larva, is strictly a leaf feeder. In spite of this 

 limitation, however, where it occurs in large numbers it can cause 



