lo; 



circumstance connected with the change to the pupa was the 

 occurrence of many pupae suspended on their threads, in which case 

 the larval skin is shrivelled up round the last segment of the pupa. 



While the favorite food plant appears to be the yellow pine 

 {Pbms ponderosd), both Phms 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 in a position to say. The search for parasitic insects was 

 not productive of either species or numbers. IchneiuncnidcB 

 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 un- 

 common, 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 par- 

 asitical pupae, although even here the percentage does not appear 

 to be very large, although they are numerically numerous; at least, 

 I judge so, from the following observations. The normal color of 

 the pupa is pale green. All those pupating on the needles of the 

 young pines or shrubby plants in the underbrush were of this 

 color, a close search failing to reveal an exception, while the 

 larger proportion of those on the bark of the large trees were 

 blackish brown. An examination of a number of these makes it 

 probable that they are all diseased, not a few containing a larva, 

 either dipterous or hymenopterous ; certainly the latter, in one 

 case at least (one pupa contained a large ichneumon nearly ready 

 to emerge, which was accidentally killed). It is somewhat strange 

 that all these dark pupj£ should occur on the bark of large trees. 

 May it not be that their diseased condition had prevented the 

 secretion of silk, and that, being thus prevented from dropping to 

 the ground in the usual way, they had wandered part of the way 

 down the tree before the final change, their restlessness being due 

 to the same cause? 



