172 

= Divide them into those attacked by the larger borers (A) and those 
.. free from them (B). Count the number in each lot attacked by the 

age. 
If the Xyleborus attacks are in no way dependent on the Viens 
of the large borers, the VOR of canes infected by it will 
be the same as of those in B. f, o the other hand, there is a larger 
Proportion of infested canes in A, it is is njanitest that either— 
. The Xyleborus follows the ‘larger borers, because they have made 
the cane suitable for it. 
T "The ca nes in A are suffering from some peculiarity which renders 
them specially attractive to both ig large and Ur small borers 
ia atin neither case if the per-centage is greater i 
“said that the attack of the Xyleborus is peris dee of ‘ihe health or 
- condition of the canes 
The Committee, strengthened by the opinion of Prof. Riley (26), 
: attribute the increase of the Xyleborus in Trinidad to the neglect to 
burn and refu Tus would, of course, favour the insects, 
but will not explain the outbreak completely, unless it can n 
that the increase has coincided with the period when the destruction of 
refuse was given up, and that in countries, as Guiana and Jamaica, 
x1 here ih in Man occurs without attracting notice asa can e-pest, the 
meg: ted that it cannot breed therein. Mere multiplication of 
the zai dies ‘of a Scolytid beetle need not involve injury to healthy plants 
if there are sickly ones to attack; but if due to increase in the amount 
of brood material caused by exceptional circumstances in any one period, 
it may bring about an attack, or an attem ted attack, in following 
|. years, when the supply of food has fallen pi Mie nor mal oo I 
these islands there is plenty of suitable broo ial, and it is remark- 
able that canes attacked by the larger borers should ever be feb from 
‘yleborus if its ipee habits are simply due to “ overerowd- 
: ve of the islands for a considerable time, 
has lived on a ies of other plants beside sugar-cane, teak: 
nce is required of very material alteration in the state of the cane- 
n the last few agi before this can be soe as the sole | 
: df its 





















namely, canes injured by other borers. Fortunately, it will not be 
- difficult to check increase arising "m such a cause as the neglect to - 
burn megass. 
Amongst the insect attacks on sugar-cane, there is one which is 
ely to be overlooked except by careful observer that of a dh which 
has been found to attack the cane in Bar "Queensla 
Mr. A. D. Michael has written an aidait. oft this animal, ‘which i is an 
"ui NO UM E GM UMANE ; 
16. Controis: 

will be Seen m the exact character of the causes which divos 
Xyleborus has not been fully determined, but requires further 
vare and. it win be well if such are made, not with the i en 
one. dioc responsible for ie attack 





