THE GIPSY MOTH AS A FOREST IXSECT. 7 



anyone associated with the Bureau of Entomolo<2;y wliicli can l)e used 

 in support of the contention that tlie disease ma}- be rendered more 

 efficient tlirough artificial dispersion. The extensive experiments con- 

 (hicted by the State of Massacl)usetts in 1912, in pursuance of its 

 policy to investigate thoroughly every possible metJiod of ridding 

 its forests of the gipsy moth, would appear to have resulted exactly 

 as did the earlier and less elaborate series conducted by Dr. Johnson 

 and others. 



NATURAL CONTROL OF THE GIPSY MOTH ABROAD. 



A large portion of the ])ost two years has been spent by the writer 

 abroad in studying the gipsy moth in its original habitat. The 

 objects of this over-sea work were several. It was desii'ed more 

 exactly to determine the part played by the parasites in holding 

 the gipsy moth in check in the European forests and to ascertain 

 whether all the important species of parasites had been discovered. 

 Were promising new species found, attempts were to be made to 

 ship large quantities to ^Vmerica for exi)erimental colonization. 

 Above all, it was hoped to learn whether the assumption upon which 

 the parasite work had originally })een undertaken was well grounded; 

 that is, whether all the factors responsible for the natural control 

 of the gipsy moth in the European forests were present and active 

 in America, saving only the parasites. The results of this work are 

 in part sui)plemented and in part confu-med by the observations of 

 Mr. L. H. Wortldey, who has spent the better part of a year abroad, 

 and in part they are pertment to this discussion. 



It was found that the mvasion of tlie greater part of Europe by 

 the gipsy moth some three to seven years ago had spent its force, 

 and that, although small numbers of the insect might be found in 

 nearly every oak forest visited in Italy and Germany, it was found 

 abundant in veiy few. It was difficult to ascertain definitely what 

 had occurred to check this general invasion, but it is certain that a 

 disease similar in all its external manifestations tt) the American 

 ''wilt" (and also to the well-known and beneficent " wipfelkrank- 

 heit" of the nun moth) had prevailed ui many localities, including 

 some in Russia, Italy, and Germany. It seemed to have been epi- 

 demic in all of the localities which had ])een badly infested by the 

 gipsy moth. 



It was also evident that following the enormous decrease in num- 

 bers brought alwut by this epidemic there was nothing like the phe- 

 nomenal increase of the straggling remainder so frecjuenth- observed 

 in America. Instead, when an innocuous minimum was reached 

 this desirable condition was maintained for an indefinite and some- 

 times for a protracted period. It a])])eared highlv probable — and tliis 

 67364°— Cir. 164—13 2 



