THE ZIMMERMAN" PINE MOTH. 7 



mature trees (see Pinipestis cambiicola, p. 6) and this is evidently 

 the reason why its activities bear no permanent fruit. Considering 

 also that the birds in hunting for the larvse strip the trees of as 

 much bark and cambium as the moth larvse destroy in one generation, 

 and that this operation is repeated each season, it is doubtful whether 

 the woodpecker cure is not as bad as or even worse than the moth evil, 

 when one considers that the brood trees are allowed to replenish the 

 ranks of the insect year after year. (PL IV.) 



The cocoon of a pirnplinid of a new genus and new species 1 is fre- 

 quently found hi the tunnels of the pine moth in Montana and Idaho. 

 In some localities this parasite kills as many as 80 per cent of the 

 larvse of the moth in second-growth trees. As the parasite cocoons 

 are not molested by woodpeckers, a full quota of this fly emerges 

 during the first warm days of each spring. While this parasite 

 greatly aids in checking the increase of the moth from larvse which 

 infest second growth, it fails, as does the woodpecker, to pursue the 

 caterpillars in the above-mentioned brood trees. Hence it is as 

 much of a signal failure as is the bird. 



Another, somewhat larger parasite (Ichneumon n. sp. 1 ) is fre- 

 quently found during winter in the chrysalis of the moth. The moth 

 does not pass the winter in the pupal stage, and chrysalids found at 

 that time always contain the parasitic fly, which, like the pirnplinid, 

 emerges during early spring. It is apparently less numerous than the 

 latter and consequently of still less economic importance. 



There seems to be justification for the conclusion that, without 

 man taking a hand by eliminating the mam propagating opportuni- 

 ties, no natural enemy of the moth will ever render it harmless. With 

 human aid these agents will accomplish all that can be reasonably 

 expected of them, i. e., the elimination of the ravages in rationally 

 managed woodlands. 



HABITAT AND HOST TREES. 



Open, sunny stands of timber are those most affected by the Zim- 

 merman pine moth. Slashings, on which reproduction has reached a 

 height of 10 feet or more, having a scattered stand of mature trees, 

 which were left standing to reseed the area or on account of being 

 unfit for logs, invariably contain the greatest amount of pine-moth 

 injury. It appears to be an absolute necessity to the insects' exist- 

 ence in a locality stocked with second growth, that the stand contain 

 some of these specimens, which constitute brood trees for this insect. 

 Where the mature timber has been cut clean over quite large areas, 

 so that the chance for influx from without is remote, the insect does 

 no damage, even though the ground may be stocked with an ideal 



1 Determined by S. A. Rohwer. 



