BULLETIN 198. THE GRAPE LEAF-HOPPER. 203 



large numbers. Certain spiders which make their webs at the crown 

 of the vine seem to depend for food very largely on the adult hoppers 

 that are caught in their webs. Ants were occasionally seen carrying 

 away young nymphs in their jaws. The ants were not long in dis- 

 covering our supply of nymphs in the laboratory, which was on the 

 second story of a building, and soon established a regular line of 

 march, where they could be seen carrying away nymphs to their nest 

 in the ground below. A small red mite was occasionally found on the 

 hoppers at Madera, but we do not know that the hoppers were actually 

 killed by this parasite. 



Fungous. It is said that a fungus belonging to the genus Epusa 

 destroyed the hoppers in Connecticut in 1890. 1 We saw no evidence 

 of fungous disease during the past two years. Neither was there any 

 great mortality of hoppers observed, except in the egg stage mentioned 

 in another place, and in this case it seemed to be due to the infertility 

 of the eggs rather than an attack of fungous disease. Since, however, 

 these insects occur in large numbers and are closely associated, once 

 a fungous disease gets a foothold, large numbers are likely to be 

 destroyed. 



MECHANICAL CONTROL. 



Blowers and Suction. On account of the habit of the hoppers of 

 flying about in the vicinity of the vine when disturbed, it was thought 

 that there might be a possibility of drawing them into a machine by 

 means of suction. A suction machine was designed and is said to 

 have worked successfully in capturing the Rocky Mountain locust in 

 1874 and 1876 when the notable outbreaks of these insects occurred. 

 This principle of suction is also used in sawmills for carrying away the 

 sawdust. 



We started out on this problem by experimenting with a ventilating 

 fan run by a gasoline engine. It was possible to draw in good sized 

 pieces of paper and other objects heavier than small insects, but the 

 distance through which the suction worked with sufficient force was 

 too short to be of any practical use against the hoppers. In order that 

 such a machine may work successfully it would be necessary to draw in 

 the insects for a distance of at least three or four feet. This might 

 be accomplished with a very much larger fan, but this would involve 

 the use of heavy machinery that would be unwieldy for use in a 

 vineyard, so that we abandoned the idea of control by suction as im- 

 practicable. 



With suction the air is drawn in with about equal force in all 

 directions from the end of the tube, so that there is not much force at 



1 Thaxter, R., Conn. Sta. Kept, 1890. 



