248 PAKASTTES OF GIPSY AND BROWN-TAIL MOTHS. 



Following these preliminary collections, which were intended for no 

 other purpose than to indicate the rate of increase, collections from 

 towns and cities to the westward of its known distribution the previ- 

 ous winter and to the northward in southern New Hampshire and 

 southernmost Maine were made. It was rather confidently expected 

 that it would be found in Maine just over the New Hampshire line, 

 and also that this would mark the limits of its distribution in that 

 direction. 



How far removed the expectations were from the reality is well 

 indicated by the accompanying map 1 (PL XXIII) , and still more by a 

 study of the table. It will be seen that instead of stopping at the Maine 

 State line, Monodontomerus has extended its range for a full hundred 

 miles to the northeastward, and that to the north and west it has pretty 

 nearly reached the limits of the present known distribution of the 

 brown-taii moth itself. But what is more surprising, it is actually 

 much more abundant in a large part of this new territory than it was 

 in Massachusetts a year before. 



It will also be observed that the distribution has been much more 

 rapid toward, the north and east than toward the west and south, 

 which is true also of that of the gipsy moth and the brown-tail moth. 

 Whether this will prove to be the rule with others of the parasites 

 remains to be seen. It is not indicated in the instance of any other 

 as yet. 



Monodontomerus appears to pass through but a single generation 

 annually. The females are sometimes, perhaps habitually, fertilized 

 before they actually issue from the pupal shell of the host. The 

 males invariably die before the winter, or at least out of many thou- 

 sands of individuals which have been secured in the winter from 

 brown- tail-moth nests at home and abroad, only females have been 

 present. Dissection of a considerable number of hibernating females 

 has failed to result in the finding of even partially developed eggs. 

 Neither has it been found possible to keep females alive in the spring 

 until eggs should develop, although some have remained in a state 

 of activity in confinement for several months. 



Beginning in 1906, and each year thereafter until 1909, numerous 

 attempts were made to secure reproduction in confinement. Dipter- 

 ous larvae and puparia as well as pupae of the gipsy moth and the 

 brown-tail moth were supplied as hosts, and females from hibernating 

 nests as well as those from gipsy-moth and brown-tail moth pupae 

 and other sources were used in these experiments. Failure resulted 

 in every instance, due, apparently, to the impossibility of keeping 

 the parents alive until eggs should be developed. 



1 The maps and tables have been prepared by Mr. H. E. Smith, to whom the work of caring for the nests 

 as they have been received at the laboratory has largely been intrusted. 



