365 



Saps and Exudations. 



anf! the imago is probably the small black and yellow beetle sent to New York 

 recently. The best remedy found so far for the borer is to put carbon bisulphide 

 or gasoline into its hole. It is best to keep one man always going about the 

 plantation with a ladder and an oil can of gasoline. He should examine the 

 trees very carefully, and take plenty of time, as he is likely to miss many 

 holes if he does not. 



A small bark beetle has given some trouble in the trees which have been 

 tapped. There are not many cases of this, but where they occur the beetle and 

 its larvae are numerous. I have exterminated the larvae with a solution of 

 sulpho-naphthol, but this does not affect the beetle. The bark beetles can be 

 dealt with by the same man who looks out for the borer, as gasoline should 

 exterminate them readily. 



A species of Noctuid Moth sometimes attacks the rubber trees. The cater- 

 pillars live in colonies, forming a nest on the under side of a leaf, and feeding 

 by night on the surrounding leaves. I have not found many of these nests, 

 and unless they become numerous these caterpillars should not be a serious 

 danger. 



At least two varieties of Sphinx Moths attack the Castilloa. One has a 

 green caterpillar which resembles the leaves in colour, and the other a gray 

 one resembling the bark. These caterpillars, particularly the green one, are 

 common on the trees ; but as there is generally only one to the tree, 1 do not 

 think they will do much damage. Both these and the Noctuid caterpillars should 

 be kept in check as long as there are plenty of birds on the plantation. 



I have not had much chance of observing the scale,* as there do not 

 seem to be many cases of it now. Places where it had been treated with 

 kerosine emulsion showed that this was effective in killing it. 



THE EFFECT OF TAPPING ON GROWTH. 



The Castilloa is a fast-growing tree. It appears to grow most quickly 

 between the ages of two and four years. The leaf surface of the tree, and conse- 

 quently the amount of liglit it gets, has a great deal to do with its growth. Shade- 

 grown trees are not nearly as large as sun-grown trees of the same age. Monthly 

 measurements of a large number of Castilloa trees show that they grow on an 

 average about a quarter-of-an-inch a month in circumference. This vaiies greatly, 

 however, the trees sometimes growing not at all for a month, and growing half- 

 an-inch or more the next month. This does not seem to have anything to to with 

 outside conditions, because different trees choose different months to do their 

 growing in. An experiment in the effect of tapping on growth does not seem 

 to show anything definite. The same irregularity of growth was noticed, but it 

 appeared to make no difference whether the trees were tapped weekly, monthly, 

 or at longer periods or not at all. I do not think the absence or presence of latex 

 in the tree affects growth one way or another, except when its absence is caused 

 by some defect in the root. 



TAPPING THE CASTILLOA TREE. 



When I first got here I tried, by a number of experiments, to increase 

 the flow of latex by multiple tapping, gradual tapping, etc., but all these failed. 

 The reason for these failures I now attribute to the shape and position of the 

 latex-carrying tissue in the plant. This tissue, I believe, is the part known as 

 the bast fibre. Bast fibres are long fibrous threads, tapering to a point on each 



* The insect referred to a scale insect belonging to the Diaspince, and is evidently Aspidiotus 

 cydonice, Comstock. This insect was originally described by Comstock from specimens found on 

 quince (Cydonia) in Florida, and is known in the United States as the "quince scale." For 

 further particulars see " Quarterly Journal, " Vol. i., No. 1, p. 19. 



