764 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



green, ovate, with a small white coronet or raised circular ridge at the top, and some- 

 what flattened on the sides that touched each other. 



The larva. — The earlier stages did not pass under review, but there is no reason to 

 suppose that they differ materially from those about to pupate, which alone came 

 under our observation. Just as the eggs were not laid on the extreme terminal nee- 

 dles, so the larva does not commence feeding on the youngest and supposedly the 

 most succulent needles, but on those which form the base of each terminal fascicle, 

 continuing its devastation towards the tip ; but even in cases where all the needles 

 have been denuded, in no case was the terminal bud touched ; indeed, the needles 

 are only devoured down to the dry sheath which encases their base. On many trees 

 all the needles were gone; on many others there yet remained a few of the terminal 

 ones, and such trees, as Dr. Hagen suggested, conveyed the idea of immense candela- 

 bra. It is evident that many of the larvJB pupate on the few remaining needles, 

 where such exist, invariably with the head uppermost; but many forsake the parent 

 tree, and these are probably such as have consumed all the food in their immediate 

 vicinity. While many larvae were fouud ascending the trunks of the larger trees, but 

 very few were found descending them, while a large number were seen hanging at 

 the end of long silken threads, swaying to and fro in the wind. Experiments on 

 these by Mr. Henshaw and myself fully proved the fact that the larva lets itself 

 down from high trees by means of this thread to the ground, abnormal as the 

 habit is among the butterflies. In one case, where the thread was fully 50 feet in 

 length, I passed my hand beneath the larva to satisfy myself that it was not descend- 

 ing a spider thread already woven (of which I had a suspicion on account of the 

 great number of threads over the bark of the larger trees), and found no connection 

 with the ground. I then caught the thread above and the larva descended gently, 

 while swaying in the wind, but detached itself directly it touched the first object. 

 Mr. Henshaw obtained the same results. Among the larvse which thus reach the 

 ground it is evident that many attempt to regain the upper limbs, for T have found 

 several trees which had been girdled by stripping off the bark over a length of some 

 four feet, and on such trees several hundred larvae had been caught on the sticky, 

 resinous surface thus exposed. Perhaps the most extraordinary circumstance con- 

 nected with the change to the pupa was the occurrence of many pupae suspended on 

 their threads, in which case the larval skin is shriveled up round the last segment 

 of the pupa. 



While the favorite food plant appears to be the jellowpme (Pimisponderosa), both 

 Pinus contorta and Abies balsamii were slightly affected, the latter much the least, 

 and it is not unlikely that these two trees will form the staple food of the next brood 

 in the districts where the yellow pines have been denuded, should it hatch during 

 the present season, as is probable. 



Enemies. — The absence of birds has already been noted. May it not be that the 

 larva is distasteful to them ? As is well known it generally happens in the case of 

 native insects that while they may gain a temporary ascendency they are ultimately 

 checked by an overwhelming army of parasites, which relegate them to their normal 

 position in nature. We might thus expect such a thing to occur in this case. 

 Whether this natural check may come into play this year or be delayed for several 

 years we are not iu a position to say. The search for parasitic insects was not pro- 

 ductive of either species or numbers. Ichneumonidw were particularly scarce on the 

 wing, both round the trees and on adjacent flowers. Indeed, the only conspicuous 

 enemy was a large heteropterous insect allied to Pentatoma, which was not uncom- 

 mon and certainly lived on the larvae, having been taken by myself in the act of 

 sucking out the nearly empty flaccid skin. Many such skins were found upon the 

 needles and on the ground around the base of infected trees. The numbers of this 

 insect, however, were apparently not sufficient to produce any appreciable result. 



Whatever hope is based on relief from parasitic insects, so far as we know at 

 present, must rest on the large number of parasitical pupae, although even here the 



