88 
Indian Forest Records. 
[VoL. IX 
For example, the most injurious longicorn borer of Shorea robusta 
is on the wing in the United Provinces from the end of June to 
beginning of September, its initial appearance and duration being 
determined by the monsoon; in years of late and scanty rains the 
danger period is delayed and reduced, whereas in wet years it is 
earlier and longer. In the moist forests of Bengal and Assam the 
flight period begins in May in conjunction with the early rains. 
The date on which a tree is felled affects its liability to damage 
by borers in so far that it is likely to be attacked first by those species 
swarming at or shortly after the date of felling. Thus, in the United 
Provinces sal felled in October to March is not subject to attack by 
the large longicorn borer (unless left in the moist shade of the forest), 
but is infested vdth shot-hole borers, sapwood borers and small heart- 
wood borers. 
Trees felled in the rains and cold weather are attacked by shot- 
hole borers, e.g., Dinpus fiirtivus, and those felled from March to 
June are not attacked. Trees felled in the hot weather are likely 
to be attacked by small longicorns : e.g., Dialeges pauper, Diorthus 
cinereus, Aeolesthes holosericea, but less so in March and April, 
when the prevalent borers would be Xylotrechus sniei and SpJiaero- 
trypes siwalikensis, species of no economic importance. The most 
favourable time to fell sal in order to ensure least damage by borers 
is in March and April. 
In Chota Nagpur two types of sal forest occur interblended, valley 
sal and hill sal, in the first of which logs lying over during the rains 
will be attacked by Hoplocerambyx, in the second of which unbarked 
timber present throughout the hot weather is liable to equally serious 
damage by Aeolesthes. 
Little is known of the sequence of borers in other trees; but it is 
evident that, in the case of refractory species, which must be seasoned 
with the bark on, a practical method of pi’otecting the heartwood can 
be found in correct fqlling-dates. The tree can be felled at a period 
when the bark and outer sapwood will be inhabited and destroyed by 
surface borers, thus producing conditions unfavourable for the estab- 
lishment of species that penetrate deeply. 
The date of girdling affects the question in an analogous manner, 
i.e., the liability to damage depending on the period at which the 
trees begin to die. In general, girdling at the commencement of the 
hot w'eather, if it produces rapid death and drying-out of the bark 
confers immunity, while girdling at the beginning of rains, unless 
the tree survives till the cold weather, presents the most dangerous 
conditions. 
The mosl favourable dates for felling and girdling require to be 
worked out by experiment for different localities, although in many 
forest divisions local practice or peculiar factors, such as labour 
supply, may have obtained satisfactory results empirically. 
[ 234* ] 
