100 



The leaves of sweet potato vines are often seen to be 

 injured when no apparent cause is noticeable. The injury 

 due to the ravages of the caterpillar are plainly to be seen, 

 and there is no doubt as to the cause of the injury ; but 



Fig. 113. Sturmina distincta. 

 Enlarged. (From Imperial Dept. Agric.) 



when the leaves merely appear unhealthy and as if the 

 plants were suffering from drought, more careful observa- 

 tion is required to enable the planter to distinguish exactly 

 the nature of the trouble. Thrips, flea beetle and red spider, 

 any one or all of these, produce an unhealthy appearance of 

 the leaves, when the minute size of the pests renders it 

 difficult to distinguish them. 



THE FLEA BEETLE (Chaetocnema amazona, Boky). 

 Coleoptera. 



This is a very small, steely blue beetle with legs well 

 developed for jumping. When disturbed the insects jump 

 from the surface of the leaf 011 which they are feeding 

 and take flight. This habit makes the flea beetle rather 

 difficult to observe. The adult beetles feed on the leaves, 

 causing them to show small patches where the tissues are 

 dry or discoloured. The feeding habits of the larvae do 

 not seem to be known. 



THRIPS (Euthrips insularis, Franklin). Thysanoptera. 



Thrips live on the under side of the leaves of the 

 sweet potato. Several species of these insects are found 

 on this and related plants ; the most abundant seems 

 to be the one named above. Their peculiar feeding habit 



