154 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



minimum. After producing such a wilt-free stock, we could then 

 rely upon individuals from such a stock for experimental purposes 

 and the results would be significant. During the season of 1915 we 

 raised several sets of caterpillars from eggs. In some sets or cultures 

 no wilt mortality occurred throughout the entire season; in most of 

 the other cultures wilt appeared, but the mortahty was low. How 

 certain individuals in these latter cultures became infected is open to 

 several explanations, the most probable of which would seem to be 

 that wilt is transmitted from one generation to another through the 

 egg. Chronic carriers of the previous generation may resist death, 

 pupate, transform and transmit the disease, as is the case with pebrine, 

 to certain individuals of the next generation. Some members of this 

 second generation become susceptible and die. That carelessness was 

 responsible for the deaths in those cultures where wilt appeared 

 spontaneously seems highly improbable for the reason that every 

 conceivable bacteriological precaution was taken. We even went so 

 far as to import daily the food for the animals from a territory which 

 had never harbored gipsy moth caterpillars. The foliage before being 

 picked was further examined for the presence of other lepidopterous 

 larvae. This precaution was thought to be necessary for the reason 

 that Chapman and Glaser (1915) found wilt prevalent amongst ten 

 of our native species of lepidoptera and the possibility of food contami- 

 nation is very great. 



In 1915 two sets of eggs were hatched. One set had its origin from 

 moths that emerged from the control experiments the previous year 

 (1914). The other set was kindly given us by Professor Richard 

 Goldschmidt, who for several years has been investigating certain 

 genetical questions in connection with the gipsy moth. Some of these 

 eggs were derived from a pure Japanese race procured by Professor 

 Groldschmidt from Ogi, Japan; others were derived from crosses be- 

 tween Japanese races with a race from Germany and one from Fiume, 

 Hungary. The caterpillars from this second set of eggs were very 

 easily distinguished from our introduced American race, by their 

 peculiar coloring and pattern. Professor Goldschmidt informed us 

 that he had had very little disease in his cultures the previous year, 

 so we thought his material ought to prove very instructive. 



Altogether a great many cultures were cared for, both American 

 and foreign. These cultures represented our stock from which we took 

 animals whenever they were needed for experimental purposes. Some 

 of the animals were immediately removed from the stock on hatching 

 and isolated, others were treated in bulk. At the beginning of the 

 season, while the caterpillars were still in the second stage, many 

 individuals died of wilt in three American cultures. These cultures 



