428 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



To the iiifestod pond 10 well-fed mallard ducks, Anas platyrhijncha, were 

 then admitted, and as they entered the pond they were first attracted by the 

 larval batraehiaus, tadpoles. They, however, soon recognized tlie ])reseuce of 

 larvie and pupre of the mosquito and immediately turned their attention to 

 these, ravenously devouring them in preference to any other food stuffs present. 

 At the end of 24 hours no pupa? were to be found and in 48 hours only a few 

 small larva; survived. The motion of the water made by the ducks, of course, 

 drowned some of the insects — what proportion can not be estimated. 



For some years I have been using ducks to keep down mosquitoes in swamps 

 that would have been very expensive to drain, but I never fully appreciated 

 the high degree of efficiency of the duck as a destroyer of mosquito life until 

 the foregoing test was made.^" 



LEPIDOPTERA (BUTTERFLIES AND MOTHS) 



When we use tlie vernacular terms butterflies and moths as equiva- 

 lents of the order name Lepidoptera we obscure the fact that it is the 

 immature stages, almost exclusively, that are of economic interest. 

 Not only are the caterpillars most important from this point of 

 view, but tliey are also most important in the food of avian predators 

 upon this order. Tliey are devoured by nearly all kinds of insectiv- 

 orous birds and are used in quantit}^ especially for feeding the 

 }'oung. They are favored for this latter purpose even by numerous 

 birds that are not highly insectivorous when adult. 



The avian attack upon the immature stages of Lepidoptera is a 

 heavy one and, as we shall see, it has resulted in numerous observed 

 cases of control or local extermination of various pests. Representa- 

 tives of 15 families of Lepidoptera are involved in these statistics 

 and they will be taken up in order. 



The larvie of a butterfly {Agraulis vanillce) of the family Nymph- 

 alidai were eaten so persistently by road runners in one case in 

 California that, according to Mr. A. W. Anthony, a fence row 

 covered with their food plant was entirely cleared of them. In 

 another butterfly family are those well-known pests, the cabbage 

 w^orms. Mr. Otto Lugger, former State entomologist, made an 

 interesting observation on their vertebrate enemies in Minnesota. 

 He had th«» ]K)sition of .500 chrysalides of (•ab])age butterflies marked 

 on a board fence and observed them through the winter to note 

 their fate; by May 1 the number had been reduced from 500 to 

 43, a destruction of more than 90 per cent, chiefly by birds. Dr. J. 

 Schneck observed in Southern Illinois one instance of complete 

 elimination of worms from a cabbage patch by chipping sparrows. 



Beginning the moths with the Sphingida^ we have on record one 

 case of local extirpation of the catalpa sphinx in Alabama by 

 cuckoos, and two of the tomato worm in Indiana by crows. One 



-.louin. Aiuer. Med. .\ssii., Vol. 0.!, No. 14, p. 1208, Oct. 3, 1914. 



