INSECTS INJURIOLS TO CUCUMBER, MELON, ETC. 



157 



The principal injury is effected by the hibernated beetles 

 devouring the tender plants before they have fairly started. 

 The beetles are also destructive to older plants, by eating the 

 leaves and gnawing the rind of stems and the fruit, while the 

 larvse cause injury through their pernicious work at the roots. 

 Still another form of mischief is due to the beetles in acting 

 as carriers of the insidious bacterial disease "cucurbit wilt." 



The beetles usually make their appearance in April or May, 

 feed on flowers or other vegetation, and when cucurbits are set 

 out attack and injure them as previously described. Eggs are 

 deposited soon after the host 

 plants are well above ground, 

 and on leaf-stalks just below the 

 surface of the ground. The 

 larval period is passed in the 

 earth, about the bases of the 

 stalks, and larvae may be found 

 within the stems under as well 

 as above ground, and there 

 is an active stage of about a 

 month's duration in which the 

 larvae working in numbers have Fig- \oz.-Celatona dwtyoticx. Fly cara- 



siteof cucumber beetles. Much enlarged. 

 ample time for mjunng the (Author's illustration, U. S. Dept. Agr.) 



Toward the end of the season the beetles congregate under 

 stems, prostrate plants and withered leaves of cucurbits, as 

 many as sixty individuals assembling about a single plant, and 

 later they seek other places of shelter. Hibernation near 

 Washington evidently begins during the first cold nights of 

 October. 



Great numbers of this insect are destroyed by a dipterous 

 parasite, somewhat resembling a small house fly, and known 

 as Cdatoria diabroticce Shim. (fig. 105), wdiich develops as a 

 maggot within the beetle, which it destroys when it issues. 



