98 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



work along even more energetic lines than in the past indicates suffi- 

 ciently well the character of the decision finally reached. 



This is not the place for, nor are the writers prepared to enter 

 into, a discussion of the caterpillar diseases of the gipsy moth and 

 the brown-tail moth, but it is perhaps not out of place to recount 

 some of the incidents which have been taken into consideration in 

 the present instance. In this, as in many others similar in character, 

 the brown-tail moth has largely been ignored, owing to its being 

 generally considered as the lesser pest of the two. As frequently 

 before, the work upon the brown-tail moth parasites, although 

 pursued quite as actively as that upon the parasites of the gipsy 

 moth, was relegated to a secondary position. 



Very little has been published concerning the gipsy-moth cater- 

 pillar disease previously to 1907, when the junior author first had 

 opportunity to familiarize himself with the situation at first hand. 

 It was to him a novelty when, early in the summer of that year, 

 wholesale destruction of the half-grown caterpillars was first noticed 

 in numerous localities before they had succeeded in effecting the com- 

 plete defoliation of the trees and shrubs upon which they were feeding. 

 In all its essential characters the disease was similar to that which 

 had swept over the army of tent caterpillars which were defoliating 

 the apple and cherry trees in southern New Hampshire in 1898, 

 as recounted in the bulletin upon the parasites of that insect, pub- 

 lished as No. 5 in the Technical Series of the New Hampshire Agri- 

 cultural Experiment Station. It was believed of this disease, at 

 the time when these investigations were being conducted, that it 

 was infectious, since the inhabitants of whole nests would all perish 

 simultaneously. At the same time, its infectious or contagious 

 nature was not established. 



On the supposition that the disease of the tent caterpillar was 

 infectious, and that that of the gipsy-moth caterpillars was similar 

 in character, it looked for a time as though the parasite work was 

 destined to an untimely end through the destruction of the gipsy- 

 moth caterpillars before the parasites had opportunity to establish 

 themselves and increase to the point of efficacy. Neither was 

 there anything observed during the summer of 1907 to render this 

 supposition untenable, except (and from an economic standpoint the 

 exception was one of grave importance) the fact that, taking the 

 infested area as a whole, there was a tremendous increase in the 

 number of egg masses of the gipsy moth in the fall of 1907 over the 

 number which had been present the previous spring. 



There did not seem to be any particular reason why the disease 

 should not increase in effectiveness as time passed on, however, and 

 when in the spring of 1908 myriads of caterpillars in the first stage 

 were found " wilting" in the forests in Melrose, and when just a little 



