Thrips injure cocoa by feeding on the leaves and pods. The 

 mouth parts of thrips are intermediate between those of insects 

 which bite off particles of food, which they chew and swallow, 

 and those of insects which are provided with a proboscis by means 

 of which they puncture the tissues and suck the juices of the plant 

 or animal tissues on which they feed. Thrips have one large 

 well-developed and one aborted or rudimentary mandible. By 

 means of the large mandible they cut or puncture the surface 

 tissues and then suck or lap up the juice or sap. Thrips feed on 

 the underside of the cocoa leaves, and generally in groups or 

 colonies. The position of these colonies is marked by a dis- 

 coloured spot on the leaf. Examination shows that the green 

 cells of the leaf have been destroyed by the feeding of the thrips. 

 When the pod is attacked, the result is slightly different. The 

 minute wounds inflicted by thrips in their feeding are healed up 

 by the growth of the pod, with the production of a dark, corky 

 material. When the pod has been badly attacked there is suffi- 

 cient of this dark-coloured material to give the pods the charac- 

 teristic mahogany or russet appearance which is characteristic 

 of thrips' attack. 



Thrips may be frequently seen with the abdomen elevated, 

 bearing at its tip a drop of excrementitious matter which is from 

 time to time deposited on the surface of the leaf or pod. When 

 this dries, it forms a very small thin flake, which helps in the dis- 

 colouration. This is however readily distinguished from the rus- 

 set appearance. 



The manner of egg laying of the cocoa thrips is responsible 

 for other wounds to the plant. The adult female is provided 

 with an ovipositor composed of two plates with saw-teeth edges. 

 Although I have not seen the actual process of egg laying, nor 

 seen it described, it seems probable that the eggs are deposited 

 in cuts or incisions made by the ovipositor in the tissue of the 

 leaf or pod. 



If the leaves of a thrips-infected cocoa tree be examined at the 

 time when the young leaves are coming out, it will be found that 

 on the young leaves there are many adult thrips, while on the old 

 leaves there will be seen few adults, and many colonies of young. 

 Both young and old are found on the pods. 



The explanation seems to be this : As the young leaves appear, 

 the adult thrips migrate to them, there to lay their eggs. In this 

 way, the eggs would be laid on the tenderest parts of the plant, 

 and the thrips larvae would have the best possible chance for 

 feeding. Probably, much the same habit prevails in the egg lay- 

 ing on the pods, although the period of growth of the pod is suffi- 

 ciently long for the development of several generations of thrips. 



The attacks of thrips on the leaves of cocoa are sometimes suf- 

 ficiently severe to cause the leaves to fall off, but on the pods the 

 effect seems to be very slight, the principal loss seemingly being 



