8 



The quantity of the salt solution used may be used several 

 times, when the basins are substantial so that they do not allow 

 it to filter, they should also be covered so as to avoid rapid evapo- 

 ration and the falling in of foreign bodies. 



Which of these processes are preferable ? It is clear that it 

 depends on the form you desire to adopt in the preparation of the 

 rubber. Should you require to obtain the milk in great quantities 

 so as to coagulate and press it, the salt solution should be used, 

 but not having the requisites then the alum process may be used. 

 One of the advantages of these two processes is the paralyzing of 

 the fermentation, preserving in the rubber all its natural qualities 

 without the disagreeable smell. They have also the advantage 

 that the rubber can be taken to the press whilst fresh, forming 

 a homogenous body and of any size required to be adopted. 



(To be continued.) 



THRIPS ON COCOA. 



By H. A. BALLOU, M.Sc, 



Entomologist on the Staff of the Imperial Department of Agriculture 



Thrips are small insects of the order Physopoda. 



They are slender, with two pairs of narrow, membranous wings 

 which are fringed with hairs. The metamorphosis is incomplete ; 

 the mouth parts are intermediate between the biting and the suck- 

 ing forms. The thrips of cocoa (Physopus rubrocincta) is from I-18 

 to 1-25 inch (1-1*5 mm.) in length when full-grown. The adults 

 are dark-brown or black, the young being pale-green or yellowish- 

 green with a bright-red transverse band across the abdomen. 



Thrips on cocoa was first investigated by the Imperial Depart- 

 ment of Agriculture In November IQOO, when Mr. Maxwell-Lefroy, 

 then on the staff of the Department, visited Grenada in connexion 

 with an outbreak of thrips. Mr. Lefroy paid a second visit to 

 Grenada to continue his investigations of this pest in March 1901 

 (West Indian Bulletin, Vol. II pp. 175-190). 



In December 1 90 1, an article by M. Aug. Elot appeared in the 

 Revue des Cultures Coloniales, entitled ' A new enemy of Cacao.' 

 This gives an account of the occurrence of thrips, in Guadeloupe 

 in 1898 and 1 90 1. The article deals with the damage done to cocoa 

 trees by thrips, the measures to be adopted for its supression, 

 and includes a technical description of the insect by M. Gaird, 

 who finding that it was new to science, proposed the name Physo- 

 pus rubrocincta, by which it is still known. The occurrence of 

 thrips in Guadeloupe is referred to in the West Indian Bulletin 

 Vol. II. p. 288), where M. Elot's report is summarized, and the 

 statement is made that 'the geographical distribution of thrips, 

 as known at present, is Grenada, St. Vincent, St. Lucia, Dominica, 

 Guadeloupe, and possibly Ceylon.' 



* Reprinted from West Indian Bulletin, Vol. VIII p. 143. 



