240 



THE GYPSY MOTH. 



thereby preventing the fertilization of scattered females and 

 the establishment of new colonies of the moth. Under the 

 most favorable circumstances in open country and with favor- 

 ing wind and weather the male will occasionally find a female 

 at a distance of half a mile. It is probable that in orchards 

 or woodlands the scent of the female does not travel so far. 

 In any case a male flying some distance to a female would 

 wander about a good deal before finding its mate. In the 

 mean time it must run the gauntlet of the flycatchers, spar- 

 rows, warblers and all the birds which so frequently capture 

 flying males. It is to these birds a shining mark, and, 

 although its flight is swift and eccentric, they readily follow 

 and easily capture it. When flying low in the open land 

 male moths are often pursued and captured by sparrows. 

 They may also be captured by swallows, but this has never 

 been observed. Experiments made in trapping male moths 

 by attracting them to females have often failed because of 

 the number of these moths captured by birds. Birds will 

 sometimes capture every male moth before it reaches the 

 trap. Therefore certain species do much in this way to 

 compensate for the injury which they or others may do in 

 distributing the moth. 



Birds versus Useful Insects, 

 In their destruction of gypsy moths birds sometimes 

 destroy parasites of these insects. The parasites within the 

 caterpillars and pupae are eaten together with their hosts. 

 Yet the immediate destruction of caterpillars by birds is 

 of more importance to man than the lingering death which 

 is caused by the parasite. The larvse of hymenopterous 

 parasites feed almost exclusively on the fatty portions of the 

 insects which they attack, thus allowing them to live, feed 

 and grow, and do as much damage to vegetation as if they 

 were not parasitized. When the caterpillar has finished 

 feeding, or later when it has pupated, the parasite, having 

 eaten the greater portion of the fatty substance, eats out 

 the vitals, thus killing its host. The bird, on the contrary, 

 snaps up the caterpillar at once, thus preventing further 

 injury to the tree. The question then arises, would the 

 parasite unhindered be more effectual in checking the rav- 



