240 INSECTS IXJURIOUS TO STAPLE CROPS. 



have not been verified in otlier parts of the country, and 

 it is improbable that am^ large ^^ortion of potato-scab is 

 due to these insects. Potato-scab is a fungous disease, 

 which, as already noted, may be destroyed by soaking the 

 seed-potatoes in a solution of corrosive sublimate. 



Some interesting oliservations have been published by 

 Messrs. Stewart and Sirrine, of the New York station, in 

 which they attribute the peculiar marking of the skin 

 known as '^ pimply^' potatoes to the larva of the small 

 black cucumber flea-beetle, Epitrix cucumeris Harris, 

 which, as a beetle, does so much injury to the leaves. 

 Without doubt this instance is a parallel to those already 

 mentioned concerning insects producing potato-scab. 

 Undoubtedly the larvae of this beetle may have been found 

 producing '• j^imply " potatoes, but several other entomolo- 

 gists and the writer have carefully examined hundreds of 

 tubers in fields fairly alive with the beetles, and at all 

 seasons of the vear, but all in vain as far as discoverins: 

 any flea-beetle larvae is concerned. 



The truth of the matter is that the natural food-plants 

 of these larv^ are some of our commonest weeds. Similar 

 instances are observed in the larva? of the Sweet-potato 

 Flea-beetle {Chceto enema confinis Clr.), Bean Leaf-beetle 

 (Cerotomatrifurcata Foerst), Tobacco Flea-beetle [Epitrix 

 parvuJa), and others which are all occasionally found on 

 the roots of the respective food-plants of the beetles, but 

 which habitually feed in the larval stage upon the roots of 

 such weeds as the horse-nettle, Jamestown weed, Des- 

 modium, and various Solonacem. In fact, the only insects 

 which are habitually injurious to the tubers are white grubs 

 and wireworms, both of which are only too familiar to 

 every farmer. So far as known, the only remedy for these 



