SWEET-POTATO WEEVIL. 63 



CHAPTER CXVI. 



SWEET-POTATO WEEVIL. 

 (Cylas formicarius, Fabr.) 

 Order : Coleoptera. Family : Curculionidoe. 



This very destructive pest was first noticed here by 

 myself as having worked havoc with consignments of 

 sweet potatoes which were being sent to Melbourne in 

 great quantities from Queensland. As the plate shows, 

 the tubers are absolutely unfit for food when badly attacked. 

 The beetle responsible for this wholesale destruction is one 

 of the Curculionidoe family, and it is somewhat ant-like in 

 shape ; hence its specific name. 



The body of the beetle is smooth and shiny, the abdomen 

 being of a beautiful steel-blue colour. The other parts 

 are mostly red-black. The rostrum, or beak, by which 

 the skin of the potato is pierced, is strong for so small an 

 insect, which is wingless. The larva, or grub, is white, 

 and about a quarter of an inch in length, and, as the plate 

 shows, it tunnels into the tubers, rendering them useless. 

 The skin is pierced by the female beetle, and in these 

 punctures the eggs are laid, and the young grubs at once 

 commence to eat into the tubers. As Mr. Tryon remarks, 

 no species belonging to the genus Cylas has so far been 

 recorded as being indigenous to Australia, so that this 

 pest is another bad importation from abroad. 



In Mr. Tryon's valuable work, he says " At present 

 (1889), I only know of its occurrence in the East Moreton 

 district of Queensland." But as the sweet potatoes which 

 we discarded here were not from the above district, it is 

 evident that the pest has spread, but to what extent I do 

 not know. When first observed in Victoria, a quick and 



