340 OPHION AUREOLATUS. 
of some being the 4th, 17th, 27th and 28th of the month. The 
lower elevation and warmer locality doubtless account for 
the flies having issued so early in the year. They probably 
normally issue from the caterpillar pupz at the beginning of 
July, which is the period when the moths appear on the wing and 
lay eggs. The ichneumon fly lays its eggs in the caterpillar 
and the young grub on hatching out feeds inside the moth 
larva but does not kill it until it has changed into the pupal 
stage. Thus the caterpillar completes all the defoliating 
damage it is capable of accomplishing before it is killed by the 
parasite. The ichneumon grub becomes full fed about Septem- 
ber, and appears to pupate during this month inside the cater- 
pillar pupa. It remains in this condition all through the winter, 
the fly issuing during the next summer. The anterior end 
of the larval pupal case splits down to allow the fly to emerge. 
Fig. 1 shows the pupal cocoon of the fly and 1a a fly just 
emerging from the moth pupal case, 
Locality from where reported, 
Mr. B. B. Osmaston took this fly in tgoo in the Jaunsar 
Forests, North-West Himalayas. 
Relations to the Forest. 
From the above account of its habits it will be seen that this 
insect is a most useful parasite. Although the grub does not 
kill off the larva it feeds upon until the latter has accomplished 
all the damage it is capable of doing, the trees thus suffering 
heavily during the year of infestation, it nevertheless, when 
rumerous, infests the caterpillars to such an extent that it is 
practically able to reduce to normal proportions any large in- 
crease in the numbers of the Acronycta pest. The 1899 and 1900 
attacks proved this, the parasite having infested the caterpillars 
to such an extent during this latter year that it was almost 
impossible to obtain any moths from the cocoons. In 1go1 
the insect was very scarce, but few larve being found upon 
the trees, This fact probably reacted upon the ichneumon 
flies, whose numbers would be in their turn reduced the 
succeeding year owing to the few caterpillars available in 
which to deposit their eggs, 
