COMMON WHITE GRUBS. 17 
It should be noted here that the giant thorn-headed worm, an 
intestinal worm attacking swine, passes one of the early stages of its 
life within the white grub,and hogs become infested with these worms 
by feeding on infested grubs. The grubs in turn become infested 
through the excrement of infested swine. In the grub-infested locali- 
ties of Iowa, Illinois, and Wisconsin visited by the writer this intesti- 
nal worm is quite prevalent, but inasmuch as most of the swine in 
these regions are slaughtered before they are 1 year old the prevalence 
of the worms in this region is of little if any importance. Precau- 
tions should be taken, however, to protect the animals from infesta- 
tion where possible. In this connection Dr. S. A. Forbes says:” 
Pigs which have never been pastured are certain to be free from these para- 
sites, and grubs growing in fields which have not been pastured by pigs are like- 
wise 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 consequences. 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.’ 
In 1912 the writer observed a field in which half of the corn was 
uninjured and free from grubs, while the other half was badly dam- 
aged. The previous year both halves of this field had been in timo- 
thy, but with this difference: The half where the injury occurred was 
left for hay and the other half was fenced off and pastured with 
dairy cows. The only plausible explanation seems to be that the tram- 
pling of the ground by the cows killed the eggs and grubs in the 
field, or else that the ground had been trampled sufficiently previous 
to the flight of the beetles to prevent them from entering the soil and 
laying eggs. 
Domestic fowls should be given the run of infested fields, and 
especially when the land is being plowed, for they are very fond of 
grubs and will destroy large numbers. 
During the years of great abundance of the beetles hogs should be 
turned into orchards and timber lots during the period of flight (May 
and June), since a majority of the beetles pass the day just below the 
surface of the soil beneath or near the trees upon which they have 
been feeding the night before, and will be eagerly sought and eaten 
by the hogs. 
2 FALL PLOWING. 
Where it is impracticable to pasture hogs in an infested field much 
good can be accomplished by plowing the land in the fall. The plow- 
ing should be done late in fall, but, on the other hand, it should not 
be delayed until cold weather sets in or until the ground becomes 
chilled and frosty, for then the grubs will have gone down to their 
1 Hehinorhynchus gigas. 
2 Forbes, S. A. On the life history, habits, and economic relations of the white grubs 
and May beetles (Lachnosterna). Ill. Agr. Exp. Sta., Bul. 116, p. 479, August, 1907. 
543, 
