^'^07.] White-gbubs and May-beetles. 



479 



corn only two grubs were found— a benefit of over 99 per cent, de- 

 stroyed by the pigs in twenty-seven days. As the grubs were at this 

 season going down to escape frost, the hogs were burrowing in 

 pursuit of them, sometimes to a depth of two feet. 



Although these pigs remained perfectly thrifty, it is proper to 

 say that there is one possibly serious objection to this very common 

 use of swine as a means of keeping in check the white-grubs in grass- 

 lands and of clearing them out of fields of corn. It has been shown 

 by Dr. C. W. Stiles, of the U. S. Bureau of Animal Industry,* that 

 one of the most injurious intestinal parasites of swine, known as 

 the giant thorn-headed worm . {Bchinorhynchus gigas), passes one 

 stage of its life in certain of the white-grubs, and that pigs become 

 infested by it by devouring infested grubs, which themselves obtain 

 it by way of the excrement of the pigs. Where either grubs or pigs 

 become infested by these parasites the situation is more or less dan- 

 gerous if pigs are allowed to eat the grubs ; but pigs which have 

 never been pastured are certain tolae free from these parasites, and 

 grubs growing in fields which have not been pastured by pigs are 

 likewise certain to be free from them. The use of such pigs upon 

 such fields would consequently be without danger from this source, 

 and a little attention to these facts will avoid any injurious conse- 

 quences. That is, if pigs not previously allowed to run out are 

 turned into fields on which pigs have not been pastured within three 

 years, there will be no danger that they will become infested by 

 these thorn-headed worms. 



The general measures discussed in my Seventh Report are es- 

 sentially^ destruction of the May-beetles before they have laid their 

 eggsPandTthe distribution among the grubs of the gerrhs of their 

 contagious diseases. Nothing has thus far been done to test the pos- 

 sibility of the collection and distribution of parasites other than 

 those of contagious diseases, and the latter subject can not by any 

 means be said to have been worked out to final conclusions. 



The May-beetles may be destroyed either by spraying repeatedly 

 with arsenical poisons the trees on whose foliage they feed; by 

 shaking or jarring them down in the cooler parts of the night from 

 the trees and shrubs on which they are feeding, and collecting them 

 for destruction ; and by trapping and killing them at night by means 

 of lanterns fastened over tubs or traps containing water covered 

 with a film of kerosene. The grubs may possibly be kept in check 

 by the distribution among them of the germs of their contagious dis- 

 eases obtained by artificial cultivation, — a method which has been 



*'*Ott an American Intermediate Host-of^cA/wor/y/^/cAwjrtVflj." By C. W. Siiles. Zool, 

 Anz.,Feb., 1892, p. 52. 



