220 THE GYPSY MOTH. 



pursue mainly the quick-flying male moths. Experience in 

 trapping male moths has shown that ordinarily their capture 

 has little effect on the number of fertile egg-clusters in a badly 

 infested spot. This is partly because most of the male moths 

 find their mates close at hand, and so fertilize females before 

 taking any extended flight; and partly because the male 

 being polygamous, each one that escapes the birds may fer- 

 tilize several females. Yet as very many of the males are 

 caught by flycatchers, this may account for the scarcity of 

 males and the number of infertile egg-clusters sometimes 

 found in badly infested localities. As many males emerge 

 before the females, and as the moth lives but a few days 

 in the perfect form, most of 

 the males usually die before the 

 females all emerge, and males 

 are comparatively scarce late 

 in the season even in a badly 

 infested locality. If at this 

 time the flycatchers and their 

 ' young frequent an infested lo- 

 cality, they still further reduce 

 the number of surviving male 

 moths. This scarcity of male 



is in part caused by the flycatchers and other birds, may 

 prevent the fertilization at that time of many eggs. Yet the 

 good done in this way by the flycatchers may be counteracted 

 by their destruction of hymenopterous parasites of the moth. 

 Of these parasites the ichneumon flies appear to be the 

 most useful, yet even they have not proved at all effectual 

 in reducing the numbers of the gypsy moth, even under the 

 most favorable circumstances. Mr. Kirkland has seen a wood 

 pewee dart down and capture an ichneumon fly, apparently 

 TJieronia melanocephala. This fly sometimes attacks gypsy 

 caterpillars, and has been frequently seen searching over 

 trees infested by them. Occasionally a flycatcher will pick 

 up a spinning larva as it hangs swaying in the wind by 

 its thread from the tree, but there seems to be no reason to 

 believe that this is a habit. Though the flycatchers confine 

 their feeding on this insect mostly to the male moths, they 



