26 PKELIMIKABY EEPORT OX ALFALFA WEEVIL. 
Cache Junction in 1910. It does, however, occur in the Bear River 
Vallej^ from Evanston, Almy, and Lyman, Wyo., northward into 
Bear Lake County in extreme southeastern Idaho. Previous obser- 
vations woukl indicate that by a natural diffusion the insect has 
spread a distance of about 30 miles each year. As a matter of fact, 
the beetles are continually being found where least expected, and 
they have not been found where, judging from their habits, we would 
feel most confident of their occurrence. 
The most rapid dispersion of the insect during the last two years 
has been toward the northeast from the original point of infestation 
in the Salt Lake Valley. Its injury is now noticeable wherever 
alfalfa is grown in the river valleys east of Ogden to the Wyoming 
State line and northward to the southern extremity of Bear Lake. 
It is known to occur, however, as previously stated, as far north as 
Cokeville, Wyo., and southward to Evanston and Lyman, where 
specimens were taken during the summer of 1911. This north- 
eastward trend of diffusion in the weevil must be considered in con- 
nection with prevailing southwest winds at the time when the beetles 
are flying, and, in fact, careful search over the newly infested territory 
seems to render it highly probable that to this cause is due this 
northeastward diffusion. The finding of individual larvae well 
scattered over Wyoming fields with little or no indications of intro- 
duction by human agencies, together with the finding of larvae in an 
irrigated valley isolated from other cultivated crops by 35 miles of 
dry desert country, are conditions hard to explain in any other way 
than that the south winds of spring and summer have resulted in 
carrying flying beetles over low mountain ranges to fertile fields 
beyond. To just what extent the winds are able to carry the adults 
into new territory is not known, but at any rate migration in other 
directions has taken place much less rapidly. 
FIELD EXPERIMENTS IN DESTROYING THE ALFALFA WEEVIL. 
Several extended series of experiments in destropng the alfalfa 
weevil were carried out at various points in the infested territory 
in L^tah, but only those that have shown the best results Avill here be 
mentioned. 
Quite naturally, a measure that will destroy a greater or less 
number of the insects and at the same time encourage the growth 
of the plant, and is of practical application, ^vill not only be the most 
attractive one to the farmer but will result in a double benefit. For 
this reason disking was looked upon as probably offering the best 
results. It was thought that by disking and spraying a more rapid 
growth of the alfalfa plants would be secured, and by following tliis 
with tjie use of a brush drag a great many of the larvae would be 
crushed and destroved. Mr. Ainslie's observations made in 1910 
i 
