46 THE SUGAR-BEET WIREWORM. 



yoiiiiij: <rr'.)win«j boets were carefully taken into consideration, but the 

 si<j:nificance 'if these points, if there is any, is too slig^ht to be notice- 

 able. While the beetles have quite a strong flio:ht, it was observed 

 that they stay relatively near their hibernating places, so the most 

 important factors at tliis period are the food and liibernating c^uarters 

 which determined their presence earlier. These conclusions were 

 arrived at from observations in fields aggregating several hundred 

 acres. These factors, however, govern dissemination under normal 

 conditions only. 



Other Factors Governing Dissemination. 



One factor wliich governs the direction of flight of the adults to 

 some extent is the wind. This factor, however, has its hmitations, 

 as the beetles can fly with ease against a very Kght breeze, and if 

 the ^^dnd is bloA\Hng too strongly they do not fly at all. 



The floods which are apt to occur during the time the beetles are 

 in secondary hibernation, or a little later, are probably of some 

 importance — at least they must be so locally, where the San Gabriel 

 River spreads over many acres of the beet fields almost every year. 

 This river flows slowly and carries much rubbish, so that a large per- 

 centage of the beetles carried along woidd ])robably survive. 



NATURAL CONTROL. 



Enemies and Checks to the Beetles. 



The adults of Limonius calijornicus, being slow in their movements 

 and conspicuous, are quite subject to the attacks of predaceous ene- 

 mies. The good work of these enemies is further helped by the fact 

 that the fields are quite bare at the time they are present in the 

 largest numbers, while the beetles are concentrated for a part of the 

 time. 



Unfortunately no figures can be given regarding the relations 

 between the birds of the beet fields and the beetles, but a few observed 

 facts may be given at this time. The only notes v/hich bear on the 

 insectivorous habits of the birds locally were taken on examination 

 of the excrement of the California shrike {Lanius ludovicianus gam- 

 heli) during the month of April. This excrement was made up almost 

 entirely of coleopterous wing covers, and of these Limonius calif or- 

 nicus and Blapstinus sp. formed about 90 to 95 per cent. A very 

 reasonable estimate woidd be that at least 70 to SO per cent of the 

 excrement examined was composed of fragments of Limonius cali- 

 fornicus. 



Many observers have determined the fact that nearly all insectivo- 

 rous birds eat difterent species of Elateridaj readily, as the latter do 

 not seem to be in the least distasteful to them. Following is a partial 



