290 



PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



reach the point of pupation, and from them a very few Zygobothria 

 adults (fig. 69) were reared. There was no ground for doubting that the 

 tachinids actually issued from the imported caterpillars of the brown- 

 tail moth and that they had actually been present as hibernating 

 larvaB within the caterpillars when they were received from Europe, 

 but at the same time the circumstance seemed so improbable as to be 

 refused immediate credence. Confirmation of the records was accord- 

 ingly sought in 1908, and preparations were made to carry large 

 numbers of the caterpillars from imported nests through to maturity 

 in the large trays, already mentioned in the discussion of Apanteles. 

 For a time everything went well, and the caterpillars passed through 

 three of the spring stages and assumed the colors characteristic of the 



last with scarcely any mortality. 

 Then, for some reason, they ceased 

 to feed freely, and began to die, 

 and even those which did feed 

 ceased to grow. Eventually prac- 

 tically all of them died, but of the 

 few which survived to pupate, a 

 very few contained the parasite, 

 and although only about half a 

 dozen of the adult Zygobothria 

 were reared, they were sufficient 

 to prove beyond question the va- 

 lidity of the earlier conclusions. 

 The death of the caterpillars from 

 imported nests in 1906 was sup- 

 posed to be due to the epidemic 

 of fungous disease which affected 

 those in confinement quite as gen- 

 erally as those in the open, and in 

 1907 death was presumed to be 

 the result of the unsanitary con- 

 ditions which resulted from the use of the closed cages. In casting 

 about for a cause in 1908, the drying of the food in the open trays 

 before the caterpillars fed upon it was deemed to be sufficient, and 

 consequently, in 1909, it was determined to use extraordinary precau- 

 tions and to rear a large number of the tachinids if it were possible. 

 In the early spring of 1909 a considerable number of the imported 

 caterpillars was dissected before they began to feed, and in some lots 

 a high percentage was found to contain the hibernating larvse of the 

 Zygobothria (fig. 63, p. 264). These lots were to be given especial 

 care, and little doubt was felt as to the success of the outcome,because 



Fig. 69. — Zygobothria nidicola: Adult female, with 

 front view of head above and side view below. 

 Much enlarged. (Original.) 



