167 
corn only two grubs were found — a beneiit 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 {Ecliiiwrhyiichiis 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 eitiier 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 tolDe 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 a destruction of the May-beetles before they have laid their 
eggs, and the distribution among the grubs of the germs 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 
*"Oti ati American Inlermediate Host of £c/iiuor/iy/ic/ius gtgas." B^- C W. Siiles. Zool. 
Anz , Feb., 1892, p. 52. 
