130 

 RECENT IN VES TIG A TIONS IN INSECT PA RA SITISM. 



By Otto H. Swezey 



(A paper read before the Agricultural Seminar, College of Hawaii, 

 February 15, 1912.) 



(Concluded) 



in the worK of introducing" parasites from foreign countries, 

 care has always been taken lest hyperparasites be introduced 

 along with them, and thus, if they also became established, lessen 

 the effectiveness of the parasite. It has sometimes been sup- 

 posed that a parasite thus taken to another country without 

 being accompanied by its native hyperparasites, would be more 

 effective when successfully established in a new -^'ace than it was 

 in its native place. The above experience has tended to modify 

 the stand taken on the question of hyperparasites, and it is 

 seen that the benefits to be derived from tne exclusion of hyper- 

 parasites are not so great as has always been supposed, and the 

 danger from their introduction is much lessened — that is, in 

 cases where there are native hyperparasites which are counter- 

 parts of the foreign ones. 



With the Tachinid flies that have been introduced, there has 

 been better success. These parasitize the gipsy-moth caterpil- 

 lars. Nine species have been colonized, some from Europe and 

 som.e from Japan. Most of these were satisfactorily colonized, 

 and at leasst two species seem to have become established, while 

 there are good hopes for some of the others. 



In the work with the Tachinids, a great deal of new informa- 

 tion was gained as to the habits of the different species of this 

 family of parasites. The ordinary method of oviposition for 

 Tachinids has been known for a long time. The adult female 

 deposits her eggs on the surface of the caterpillars ; they hatch 

 and the young maggots penetrate the body of the caterpillar to 

 feed upon the fat-bodies, juices, and eventually the vital organs; 

 then, when full-grown, they emerge to pass through the pupal 

 stage in the ground. Among the species studied at the Gipsy 

 AToth Parasite Laboratory, were some that were found to have 

 different habits from that, so a careful study was made of the 

 habits of all of them in so far as possible. Sasaki, a Japanese 

 entomologist, had, about twenty years previously, in studying the 

 parasites of the silkworm, ascertained that a Tachinid doix^sitcd 

 its eggs on the leaves. When eaten by a caterpillar feeding on 

 these leaves, they hatched inside the alimentary canal, bored 

 through its walls, and located for a time in ganglia. Later on, 

 they became fixed with the posterior end in close connection with 

 spiracles and feeding on the juices and fat of the caterpillar, 

 eventually killed it. 



