Part L] Beeson : Life-History of Diapus furtivus, Sampson. 10 
Tlie figures in the table show that emergence of mature beetles 
commenced in the fourth week of October, and continued steadily until 
the middle of November, after which the daily numbers decreased and 
a weaker emergence occurred until the end of the month. In Decem¬ 
ber a few belated individuals appeared irregularly during the first fort¬ 
night, the last emergence occurring on the 15th of the month. The 
tree was examined on the spot on 18th January 1915 and was found 
to contain no Diapus furtivus. A comparison of the two logs, one of 
which, A, was removed from the forest on the 29th August, and the 
other, B, on the 27th September, shows that, while the attack of Diapus 
furtivus commenced as early as the middle of August, the bulk of the 
swarms did not arrive at this particular tree until early in September. 
Assuming that the prolonged emergence period of 5 or 6 weeks is paral¬ 
leled by an equivalent period of attack, it is evident that the period 
of development of an average individual from egg to flight is 10 or 11 
weeks. The tree, however, remained in a favourable condition for the 
development of several broods throughout a period of 16 to 18 
weeks. 
The emergence records obtained under insectary conditions were 
confirmed by actual observations in the field in 1913 and 1915. In 
November 1913 the writer toured in Buxa Division, Bengal, and found 
Diapus furtivus abundantly throughout the month. The species was 
taken on the wing, swarming, egg-laying, and boring its galleries in the 
sap-wood. That the flight period is very prolonged may be concluded 
from the fact that while eggs and early stage larvae were found on the 
12th November, in galleries which had been excavated to a length of 3 
or 4 inches, large numbers of beetles were taken on the wing from the 
14th to the 20th swarming round felled Sal trees. 
Again, in December 1914, in the course of a tour in Jalpaiguri 
Division, Bengal, Diapus furtivus was found in various stages of develop¬ 
ment, on the 5th in a tree dead some months. In the upper part of the 
bole, where the attack usually commences, maturing broods of the borer 
were present with old larvae in the galleries, and pupae and young 
beetles in the pupal chambers, while lower down the bole less advanced 
stages were predominant. 
Again, on the 13th December, in a tree known to have died in August 
(S. T. 10), the work of Diapus furtivus was found extending from the 
top to the bottom of the trunk. In the upper parts of the bole the 
broods had matured and the beetles swarmed, while the lower part of 
the tree still contained pupae and beetles in the pupal chambers. On 
the 15th December in a standing dead tree (S. T. 15), the borer wa3 
[ 19 ] 
