131 



Among the species studied at the laboratory, this method of 

 oviposition was found, as well as several others. One species 

 was found to deposit living maggots on the surface, another 

 beneath the skin of the host caterpillar ; and one deposited liv- 

 ing maggots on leaves where they awaited a convenient oppor- 

 tunity to attach themselves to a caterpillar and penetrate its body. 

 There are now known to be these five methods by which young 

 Tachinids gain access to their host caterpillars : host-oviposition ; 

 leaf -oviposition ; supra-cuianeous host-larviposition ; subcutaneous 

 host-larviposition ; and leaf-larviposition. 



Another matter of great interest was brought out in these in- 

 vestigations — that is, that many Tachinids are physiologically re- 

 stricted in their host relationships. For instance, if larvae of any 

 Tachinid gained access to a caterpillar in any of the above men- 

 tioned ways, conditions might be found such that they might, 

 fail to develop, if the conditions, chemically or physiologically, 

 v»'ere different from those in their own special host. It is for 

 such reasons probably that many parasites have come to have 

 such intimate correlation with certain hosts that they cannot sur- 

 vive or thrive satisfactorily on any other host. Hence, in the 

 consideration of the introauction of parasites, the most valuable 

 onec would be those thai were restricted or closely corrected 

 with the particular host that they are desired for, other circum- 

 stances being favorable. 



Several Hymenopterous parasites of gipsy-moth pupae have 

 been introduced. One of them {Monodontouicnis) has become 

 established, and very widely spread throughout the region infest- 

 ed by the Gipsy Moth- Investigations show that it has spread at 

 the rate of ten miles per year. After colonization of this species 

 had begun, it was pronounced a hyperparasite by Dr. Ashmead ; 

 colonization was then stopped, even though they were emerging 

 in large numbers from imported parasite material under condi- 

 tions which pointed toward it being an important primary para- 

 site. Later investigations showed that it was chiefly a primary 

 parasite, even though it was also sometimes a secondary on Tachi- 

 nids and others. Colonization was again resumed, with the result 

 that it is now the most widely spread of all the parasites that 

 have been introduced. In fact, it has been found spread nearly 

 throughout the infested region. It attacks Brown-tail Moth 

 pupae to a greater extent than it does Gipsy Moth pupae. It 

 has also been found to attack pupae of native moths. As a hy- 

 perparasite, it has been bred from Tachinids and from the co- 

 coons of the Braconid. Apantclcs. 



Many of the parasites that I have found so far mentioned, at- 

 tack both the Gipsy Moth and the Brown-tail Moth. Besides 

 these, other parasites have been investigated and their introduc- 

 tion attempted, which attack the Brown-tail Moth and not the 

 Gipsy Moth. Some of these have been more successful than 

 those on the Gipsy Moth. 



