METHODS OF TRAPPING INSECTS 85 



of the cocoa tree in the early morning. At this time of 

 day they are easily caught and can be killed by throwing 

 them into a vessel containing a mixture of water and 

 kerosene. 



Surinam cocoa planters trap these beetles by tying 

 large pieces of the bark of the silk cotton tree to the 

 trunks of the cocoa trees, to provide a hiding-place for 

 them. 



These traps are examined during the day-time, and 

 large numbers of beetles are caught by this means. 



Branches cut from the trees are left on the ground in 

 Grenada for two or three weeks. The adult beetles lay 

 their eggs in these branches, but these are destroyed as 

 the branches are burned. Although it is comparatively 

 rare to find a tree which has been killed outright by this 

 beetle, its attacks seriously interfere with the health of 

 the tree. 



In Grenada it is reported (Journal Royal Society of 

 Arts, August 13, 1909) that on one cocoa estate, 200 acres 

 in area, 120,000 beetles, larvae, and pupae have been 

 killed in a year at a cost of 50 ; and on a neighbouring 

 estate 200,000 were accounted for. 



Another beetle (Adoretus unibrosus) is reported to feed 

 upon the leaves of the cocoa trees in Fiji, but is not 

 very destructive. 



Preuss reports that the larvae of a Longicorn boring 

 beetle (Tragocephala senator ia) is destructive to cocoa 

 trees in Kamerun. 



Thrips. These minute insects are destructive to 

 cocoa trees in most countries where it is grown, and 

 especially when the trees are suffering from drought, 

 lack of proper plant-food, or other causes. Ballou de- 

 scribes a species of thrips, Pliysopus rubrocincta, common 

 in West Indian cocoa plantations, as follows : " The 

 adult insect is from -^ to T V in. in length ; it is dark brown 

 or black, with delicate wings, which are fringed with 

 fine hairs. The young, which have no wings, are pale 

 green or yellowish green, generally with a bright red 

 band extending across the abdomen." These insects 

 attack the foliage and fruit ; they are usually found on 

 the under surface of the leaves in small colonies. An 

 affected leaf is discoloured even on the upper surface, 

 and if the thrips be numerous it is killed. In the case 



