BUREAU OF ENTOMOLOGY. 499 



eat the leaves at first and spin down to the ground, where they feed 

 upon underbrush and scrub oak until they reach a very considerable 

 size. Having reached this size, they climb into the more resistant 

 trees and are at that stage able to eat their leaves. As the result of 

 this season's work it seems entirely possible to keep large bodies of 

 woodland in perfectly good condition and well stocked with trees by 

 the destruction of the underbrush and of the trees preferred by the 

 caterpillars. The woodlot in Metheun, referred to above, contains 

 an admirable stand of timber, and will probably not be harmed by 

 the gipsy moth if some pains are taken to keep down scrub oak and 

 other underbrush. 



IMPORTATIONS OF USEFUL, INSECTS. 

 IMPORTATIONS OF INSECT ENEMIES OF THE GIPSY MOTH AND THE BROWN-TAIL MOTH. 



The work of introducing the parasites and predatory enemies of 

 the gipsy and brown-tail moths has been continued throughout the 

 year in cooperation with the State of Massachusetts, and during the 

 midsummer a force of 37 men was employed to carry on the work 

 at the laboratory and to make the necessary investigations in the 

 field. 



At the close of the fiscal year 1910 it was found that all the spe- 

 cies of parasites which could be secured from importations of brown- 

 tail moth hibernating nests had already been liberated and had be- 

 come established to such an extent as to warrant the discontinuance 

 of further importations of this kind. The results of later work have 

 amply justified this course, and it has been very encouraging to find 

 that all of the parasites which have been introduced in this way have 

 reproduced and dispersed in a very satisfactory manner during the 

 past season. 



By means of a careful system of making field collections and checking 

 up the spread of various imported species in the infested area in New 

 England, it has been found possible to determine the present range 

 of many of the introduced species. Monodontomerus cereus, which 

 attacks the gipsy and brown-tail moths in the pupal stage, and which 

 was found a year ago in nearly all of the towns between Boston and 

 the New Hampshire line, has dispersed widely and is now to be found 

 over practically the whole of eastern Massachusetts, in several towns 

 near Providence, R. I., through the southern part of New Hampshire, 

 and has extended into eastern Maine to a point nearly halfway be- 

 tween Portland and Bangor. Pteronialus ef/fegius, a species which 

 destroys brown-tail caterpillars in the winter webs, has been found 

 in small numbers over a widely scattered area in Massachusetts, New 

 Hampshire, and Maine. Two of the most promising parasites that 

 attack brown-tail moths, namely, Apanteles lacteicolor and Meteorus 

 versicolor^ have greatlv increased their range during the past year. 

 The former has been found over approximately four times as much 

 territory as that occupied a year ago, and while the latter has not 

 been secured from as many additional towns, the increase is satis- 

 factory, owing to the extreme difficulty of recovering the species in 

 the field unless it occurs in considerable abundance. 



One of the tachinid flies, Zygohothria nidicola^ mentioned in the 

 previous report, which destroys brown-tail caterpillars when they 



