128 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



being of the forest to such small numbers as to require several years 

 at least before it would be possible for such conditions to recur. 



The investigations having been conducted in September, some time 

 after the death of all of the caterpillars and pupse, it was no longer 

 possible to determine with assurance the cause for the peculiar condi- 

 tions, but everything conspired to indicate .that nothing less than an 

 epidemic of disease had been responsible. The condition of the 

 pupal shells which hung upon the trees in countless thousands was in 

 every respect identical with the condition of the pupal shells which 

 are to be found in Massachusetts in every locality where the disease 

 has prevailed to a destructive extent the season before. Among the 

 old egg masses which plastered the extreme base of nearly every tree 

 in most of the localities visited were found a variable, and sometimes 

 a very large, proportion which had hatched only in part or not at all. 

 The appearance of these unhatched masses was identical in every 

 respect with the appearance of similarly large numbers which are 

 frequently found in Massachusetts. The reason for the nonhatching 

 of the eggs is not yet plain, but it is the consensus of opinion that this 

 is probably associated with the "wilt" disease. It is known that 

 affected caterpillars may pupate before death, and it seems not illogi- 

 cal to suppose that slightly affected caterpillars may pupate and 

 produce moths which are able to deposit their eggs, but that these 

 eggs fail to hatch as the direct result of the taint in the blood of 

 their parent. 



These Russian experiences seem, on the whole, to indicate that 

 in that country the gipsy moth is not controlled by its parasites to 

 an extent which serves to remove it from the ranks of a destructive 

 pest. But as one day after another in the field at Kharkof served 

 more and more indelibly to deepen this conviction, it served equally, 

 first to create, and finally in retrospect to confirm, the observer in 

 another, which was, in effect, that if this was the best that could be 

 expected of disease as a factor in the control of the gipsy moth in its 

 native home then something better than disease must be found to 

 control it in America. Just so long as conditions similar to those seen 

 in Kharkof or pictured in the letters of Prof. Kincaid are allowed to 

 prevail in Massachusetts just so long will the incentive remain to see 

 the parasite-introduction experiment carried on until success is either 

 achieved or proved impossible. Conditions similar to those prevail- 

 ing in Russia emphatically do not prevail in western Europe, nor, 

 according to all accounts, in Japan. Natural conditions in western 

 Europe and in Japan are in many respects more like those of our own 

 Eastern States than are those of Kharkof Province. Conditions in 

 Kief Province, even, are much more like those of Massachusetts than 

 are those of Kharkof, and in Kief parasite control seemed to be an 



