Part III.] Beeson : BeeKole Borer of Teak. 55 
The Girth-Beehole Incidence. 
[Vide Diagram 1.] 
For each sample plot the arithmetic mean number of beeholes per 
girth-class and the arithmetic mean girth for that class is determined. 
Where adjacent girth-classes show very divergent means, as may occur 
with small numbers of sample trees, adjustment is made by grouping 2 or 
more girth-classes together. The beehole values are plotted as ordinates 
against the corresponding girth values as abscissae, and a curve drawn 
with reference to these points. This curve shows the probable number 
of beeholes occurring in an average tree of given girth in the area 
sampled. 
The Girth-Beehole Incidence curves obtained in the sample plots 
recorded in this note are shown together on the same scale in Diagram I. 
It will be seen that in all there is a constant upward tendency, which 
in the older plots becomes very steep. Each curve was drawn as soon as 
the data were obtained in 1918 and 1919, without reference to the other 
curves. The marked parallelism, which appears when all curves are 
plotted together, is therefore intrinsic and not due to personal equation. 
By the graph method the curve of any one set of observations is directly 
comparable with that of another set, whether the trees analysed be of 
normal or abnormal growth, or the several plots of different ages, 
provided the individual plots are even-aged. In mixed stands of 
uneven age, interpretation, though possible, is more difficult. Any 
sample plot of which the curve lies vertically above that of another 
plot may be described as “ more badly attacked,” or, more correctly 
phrased, has, on an average, a greater total number of beeholes per tree 
girth for girth. 
From the girth-beehole graphs it is evident that the number of beeholes 
per tree is directly proportional to its girth in a stand of even-aged 
trees, and that the number of beeholes also increases with age but at a 
different rate for each girth. In order to make absolute comparison 
of plots of different ages it is necessary to eliminate the girth factor, and 
express the intensity of attack by an index based on the beehole-age 
relationship. 
The Age-Beehole Incidence. 
The only available data on the relation between Age and Girth in 
teak plantations in Burma is contained in Diagram III of Forest Bulletin 
[ 283 ] 
