62 
DISTRIBUTION AND MIGRATIONS OF THE MORMON CRICKET 
(ANABRUS SIMPLEX Hald.) IN COLORADO. 
By S. ArtTHUR JOHNSON, Fort Collins, Colo. 
During the past summer there was a serious outbreak of the Mor- 
mon cricket in Colorado. The writer spent about two weeks in the 
infested part of the State, where he collected many data and made 
observations on the life history of this insect. It has been thought 
best, in this account, to give, in the first place, a brief summary of 
the facts obtained in each locality; second, to attempt to trace the 
great waves of migration: and, third, to give a summary of this 
information. 
Axiel, a town in Routt County, Colo., just north and east of the 
Danforth Hills, was the nearest point we reached to what appears 
to be the established home of Anabrus simplex. A lady living on a 
ranch 7 or 8 miles east of Axiel says that it is necessary to fight the 
insects almost every vear. The armies come in from the west and 
travel east and up canyons. The migrations appear to begin soon 
after the eggs have hatched and continue until egg laying begins | 
again, when the insects locate on the dry hills and devote their ener- 
gies to providing for their offspring. The pest is kept off the crops 
here by herding or driving and making noises. 
At Hamilton, a town perhaps 20 miles east of Axiel, on the Wil- 
hams Fork of Bear River, the migrations are less frequent, and we 
were able to obtain definite data regarding them. The first observa- 
tion was made by Mr. T. H. Hamilton and occurred in 1879. Nothing 
more was seen of the insects until 1895, when a second migration is 
recorded. Again, in 1900 and 1902, hordes of the insects passed 
through. In these visits they took all kinds of garden and field 
crops. Climbing the trees, they collected on the limbs until these 
bowed with the weight of insect life. The migration from here in 
each case was northeast. A glance at the map (fig. 6) will show that 
the direction of their travel took them immediately into the Williams 
River Mountams. To accomplish this they were obliged to cross 
the Willams Fork, which flows with considerable speed at this place. 
Tmmense numbers were drowned in the attempt and floated down the 
stream. In one case they came in contact with an obstruction and 
formed a temporary dam to the water. According to the observa- 
tions of Mr. Hamilton, the insects traveled about 30 miles in two 
years. In each case when a brood has passed through, eggs have 
been laid in this locality. They hatch early in the spring as soon 
as the snows melt (March or early April). The young are not injured 
by the rigors of the season. Frequently they are frozen stiff during 
