TACHINID PARASITES OF THE GIPSY MOTH. 207 



XVII, fig. 2, at right), about 8 inches in diameter and 12 inches high, 

 with wooden top and bottom. His best results were secured through 

 the use of this cylinder, and the reason appeared to be that the flies 

 were less likely to fly and acquire sufficient momentum to injure 

 themselves in small than in large cages. 



In elaboration of the principle apparently involved, a still smaller 

 cylinder (PL XVII, fig. 2, at left), scarcely 3 inches in diameter and 

 snorter than that formerly used, was experimented with. Better 

 results than ever before were secured upon the single occasion upon 

 which this cage was used, and unless further experimentation results 

 in additional modifications or in a reversal of the results first obtained, 

 the cylinder cage figured herewith will be used almost exclusively 

 in 1911. 



As a basis for comparison of the utility of the large versus the 

 small cages, the results attending the investigations into the biology 

 of Blepharipa may be taken as an example. 



Between 300 and 400 flies were used in an attempt to secure 

 opposition in the large cage in 1908, and no care that could be given 

 them under these conditions was lacking. Not a single female com- 

 pleted her sexual development to the point at which she was capable 

 of depositing fertile eggs, and no eggs of any sort were secured. 

 Scores instead of hundreds of flies were used for the experiments 

 in the spring of 1910, and many of the females lived throughout 

 the period allotted for the incubation of their eggs and deposited 

 them at the rate of several hundred daily, and abundant opportunity 

 was thus afforded for the continuation of the studies into the fives 

 and habits of the young larvse under different conditions and in 

 different hosts. 



In short, after the most thorough tests, the use of the large out-of- 

 door cages has been definitely abandoned for all phases of the work 

 at the gipsy-moth parasite laboratory. It is not, however, intended 

 to state thus dogmatically that similar large cages would not be 

 adaptable to work with parasites of any other host. 



HYPERPARASITES ATTACKING THE TACHINIDS. 



Undoubtedly there is abroad an important group of secondary 

 parasites of the gipsy moth and the brown-tail moth, included in 

 which are some which attack the various species of tachinids to such 

 an extent as indirectly to affect the welfare of the primary host. 

 Very little is known of this hyperparasitic fauna, because practically 

 all of the tachinids received have been from host caterpillars which 

 were living at the time of collection. That it exists is well indicated 

 by the tentative studies of the American parasites of Compsilura 

 concinnata, which were made in 1910, and which will be the subject 

 of mention at another place. 



