PEELIMIHAKY EEPOET O^ ALFALFA WEEVIL. ^5 
MIGRATION AND DIFFUSION. 
There are two periods during wliich the adidt insects migrate, more 
or less aided by the winds and perhaps to a less extent by other 
agencies. Such as have not liibernated directl}- in the alfalfa fields 
become active in early spring and fly about freely, seeking 
such fields in wliich to deposit their eggs. This spring migration 
covers a considerable period of time — about six weeks, as estimated 
by Mr. Titus. As the females are more or less heavily laden with. 
eggs, however, the flight of the indi^^dual is perceptibly shorter than 
in the second, or summer, migration, the season for wliich begins 
early in June and continues for three or four weeks. Another reason 
for the shorter flight in spring is that the beetles are searcliing about, 
not for places of liibernation, but for breeding places. Having found 
these, they naturally would not go farther unless carried by the 
\\dnds. In case of a summer flight, however, the conditions are 
altogether different. This is the season during which most nomadic 
insects become more Tvidely diffused. At this time the beetles fly 
high in the air and apparently over long distances. They are also 
to be observed crawhng about in almost every situation, as with the 
larger species, Hypera punctata, wliich naay be observed wandering 
aimlessly over the pavements in the midst of large cities. Then, 
too, they appear to float about freely on the surface of water, and 
are doubtless carried long distances down stream by the current. 
We know this is true in the case of irrigating ditches and canals, and 
it is also true of the larger species just mentioned in case of streams 
in the East. Tliis habit of the beetles in liiding themselves away in 
any crevice or aperture that wiU accommodate them doubtless has 
considerable to do ^^dth their diffusion. As a matter of fact, how- 
ever,, it is absolutely impossible to lay down an}^ law that appears 
to regulate the diffusion of the insect. There are instances where it 
would seem almost impossible to prevent the distribution of the pest, 
and 3^et most careful examination has failed to reveal anj^thing of 
this sort. For a considerable time after the alfalfa weevil became 
abundant about Salt Lake and Murraj^ hay was shipped from these 
points to Elj^, Nev. Tliis, too, in the midst of the season, when it 
would seem impossible to transport hay from these points to its 
destination ^\^thout carrjdng greater or less numbers of the weevil. 
Not\\dthstanding this, years have gone by, and during the summer 
of 1911 two assistants examined the country about Ely most care- 
full}^ ^vithout finding a single alfalfa weevil or any indications that 
it had ever existed there. ^Tiiile it is possible to account for the 
spread of the insect theoretically, we can not as yet account for its 
diffusion to the northeast into adjacent sections of Wyoming and 
Idaho. It does not appear to have entered Idaho by way of the 
Cache Valley, although Mr. Titus found beetles on a coal car at 
