White Grubs 



LIFE HISTORY 



The life histories of the May beetles are not very well known. Few 

 records exist of the raising of beetles from the egg. In all probability 

 most, if not all, of the injurious species occurring in the beet growing 

 sections of the arid West have a three year life cycle. It is possible that 

 the same species may complete its development in two years in the South, 

 in three years in the northern tier of states, and require four in Canada. 



In general, the life cycle of the white grub is as follows : The beetles 

 lay their eggs in the soil in early summer. As soon as the young grubs 

 hatch they begin to feed. At this time they seem to prefer decaying 

 vegetable matter, although when very numerous they are known to 

 attack and damage growing crops. Feeding continues until the approach 

 of cold weather, when the grub burrows deep into the soil, where it spends 

 the winter in hibernation. Usually the damage done during the first 

 season of the grub's life is slight. 



With the return of spring the grubs come toward the surface, where 

 they begin a season-long campaign against the farmers' crops. It is 

 during this second year of their lives that the grubs do the most damage. 

 At this age the grub appears as in Figure 19, Plate I, Page 11. 



Again with the coming of winter the grub burrows into the soil, 

 returning to the surface the following spring to feed a few weeks. The 

 change from grub to pupa takes place about the first of June. After 

 remaining in this resting stage for several weeks the adult beetle emerges 

 from the pupa. The beetles do not leave the soil until the following 

 spring, however. Digging their way out of the soil during May, the 

 beetles proceed to feed, mate and deposit the eggs for another generation 

 of grubs. 



Figure 23, Plate I, Page 11 represents the adult of a common white 

 grub which sometimes occurs in fields in our river bottoms. 



Figure 20, Plate I, Page 11 is the grub of a small species which is 

 found in newly broken alfalfa ground and is often mistaken for the young 

 grubs of injurious species. So far as known it feeds only upon rotting 

 vegetable matter and not upon crops. 



NATURAL ENEMIES 



The white grub is preyed upon by many birds, animals and insects, 

 which materially aid in holding it in check. The U. S. Biological Survey 

 has found this insect in the stomachs of 60 species of common birds. Of 

 the feathered enemies of the white grub the crow and the crow blackbird 

 are no doubt the most important. Both of these birds will follow the 

 plow in grub infested fields and search out the grubs exposed. The 

 number of grubs which a crow blackbird will eat at one time is almost 

 beyond belief. It has been reported* that one bird ate 20 grubs in about 

 two minutes. 



Skunks are very fond of white grubs. Meadow lands are often so 

 thoroughly worked over by these animals that hardly a square yard over 

 large areas does not contain one or more of the shallow holes from which 

 a grub has been taken. 



*J. J. Davis, "Common White Grubs." Farmers' Bulletin No. 543, U. S. Department of Agricul- 

 ture (1913). 



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