60 THE EEPORT OF THE No. 36 



on thorn, and so on clown the list, whilst only a very small per cent, were found on 

 pear, plum and willow. In the case of pear and plum the explanation is readily 

 found in that, whilst these trees are plentifully grown in ^Massachusetts they are 

 rarely met with in iSTew Brunswick. In the case of willow, however, the same 

 explanation will not hold, as in the Province of New Brunswick willow trees are 

 quite plentiful, especially along the hanks of rivers and streams, and the species 

 are almost certainly the same as those found in Massachusetts — yet only one nest 

 out of a total of 2,45'2 was found on willow ! 



Two reasons for this suggest themselves, one of which is found in the origin 

 of the New Brunswick moths. It has been abundantly established that the pre- 

 vailing north-easterly winds have played an important role in the distribution 

 of the pest on the North American continent; and moreover it is reasonaJble to 

 suppose that moths hatched out on high lands have been more subject to this 

 method of distribution than those hatched out in valleys and sheltered places. 

 The primary supply of moths in New Brunswick was therefore probably blown into 

 the country from the high lands or 'ridges' of the adjoining State of Maine. The 

 host plants on these high lands are conspicuous, arguing from the similar conditions 

 of Charlotte County, New Brunswick, by an absence of willow, and would be 

 made up largely of apple, bilberry, choke-cherry and thorn. This at least partially 

 accounts for the absence of New Brunswick nests taken on Salix. 



Another reason may probably be found in the tendency of the moths to breed 

 back or lay their eggs upon a host plant of the same species upon which their 

 respective caterpillars were reared. This 'breeding back' is a well-known and well- 

 established trait among certain Lepidoptera with a choice of food plants, and 

 there seems no reason for supposing that E. chrysorrhoea is not subject to the 

 tendency. If the insect is subject to the tendency it would not be expected, in 

 view of the scarcity of Salix in the localities from which the New Brunswick 

 supply of moths originated, that willow would be selected as yet in the Province 

 as a food plant. 



These two factors working either separately or more likely together seem to 

 be sufficient to account for the peculiar difference in the food habits of the moth in 

 New Brunswick and Massachusetts. iVs the insect increases in the Province, and 

 food plants become relatively scarce there M-ill probably be developed a strain 

 depositing eggs on willow — and also on elm. 



Before leaving this subject of host plants it may be pointed out that just 

 as the lack of nests found on Salix can be explained so and in precisely the same 

 manner can the abundance of nests found on apple, bilberry, thorn and choke- 

 cherry be explained. From these four host plants was bred the original stock that 

 was blown into New Brunswick; the moths found themselves blown onto the 

 'ridges' of Charlotte County where plants of the same si>ecies were abundant; the 

 tendency to breed back onto the original host plants was present; and the result 

 was that 97.61 per cent, of all the nests found in N. B. in the winter of 1911-13 

 were taken on apple, bilberry, thorn and choke-cherry. 



In regard to the Qgg laying capacity of E. chrysorrlioea, there was found to be a. 

 decrease in New Brunswick as compared with Massachusetts of 110 less eggs 

 per female. In 1907, Mr. A. H. Kirkland* had 389 winter webs collected at 

 various points throughout the then infested district and examined; these gave an 



*A. H. Kirkland, Third Annual Report of the Superintendent for Suppressing the 

 Gipsy and Brown-tail Moths, Boston, 1908, pp. 168-169. 



