44 



THE SUGAR-BEET WIREWORM. 



after the first rains, is quite thorougli, averaging from 10 to 14 inches 

 diH'j), and as the soil is damp and mellow at this time very few clods 

 are left. This treatment disturbs most of the beetles, and these, 

 unless the weather is too severe, may come to the surface and fmish 

 their hibernation in any sheltered place they can find. If the weather 

 is severe and cold many of the beetles prefer to remain in the soil. 

 It is due to these conditions that there is a variation in the time of 

 appearance of the adults, as has been proven by systematic collec- 

 tion in the fields. 



Collections were made in some of the fields day after day and 

 tabulated. The beets which sheltered adults every day were marked, 

 and the beetles which were collected from them every day were 

 noted. The following table gives the number of beetles which were 

 taken from under the same beet on the dates given: 



Table I. — Emergence of adults of the fiugar-beet ir ire norm from hibernation in the field. 



As these notes were taken before the beetles were m()\-ing through 

 the field very generally, it appears that the latter must liave come 

 from the soil near the beets wliirh were used for hibernating quarters. 



, Secondaky Hibernation. 



The beetles which are driven to the surface prematurely seek what 

 may be termed "secondary hibernation" under alm(,st any shelter 

 which can be found. The substances in the following Mst, under 

 which beetles were found, are named in about the order of prefer- 

 ence: 



(1) Left-over beets. 



(2) Old beet tops. 



(3) Wild beet roots. 



(4) Alfalfa roots. 



(5) Johnstm <^rass roots (Sorr/lntm hole- 

 ])ense) . 



(6) Lainbsfiuarters {('hntopodium sp.). 



(7) Pigweed stalks {Amaronthus relro- 

 fiexus) . 



(8) Wood. 



(9) Clods. 



(10) Cracks in soil. 



(11) Old sacks. 



(12) Manure. 



(13) Miscellaneous rubbish. 



