112 APPLIED ENTOMOLOGY 



after a month or two, but the beetles remain in these underground pupal 

 cells until the next (fourth) spring, when they emerge. The length of a 

 generation as thus outlined therefore is 3 years, but the progeny of any 

 given beetle appearing one spring will appear the spring of the fourth year 

 following, i.e., a generation requires 3 years but is present in parts of 4 

 calendar years. 



This life history holds for most of the injurious species of June bugs 

 in the Central States, through the country east of the Rocky Mountains. 

 In the North, however, the life history in some cases at least, requires 4 

 years, while in the Southern States 2 years appears to be the normal period. 

 Some appear every year though, indicating the existence of three broods 

 in those regions where the 3-year life-history exists, but the size of these 

 broods is markedly different. Though undoubtedly subject to factors 

 which may increase or decrease the size of these broods as years pass, the 

 most abundant and destructive one at present is that in which the beetles 

 appeared in 1917 and 1920, and which will reappear at 3-year intervals 

 hereafter, the greatest destruction being caused by the grubs the following 

 year. The second brood, the beetles of which appeared in 1918, was not 

 of sufficient size to attract much attention by their injuries in 1919 and 

 probably will not be important in 1922, while the third brood with the 

 beetles in 1919 and their injuries in 1920 was of importance in only a few 

 areas. How soon favoring conditions may lead to one of these last-named 

 broods becoming large enough to be important, or unfavorable factors 

 reduce the importance of the first-mentioned one, cannot be predicted. 



Though white grubs have many natural enemies, including numerous 

 mammals, birds and insects, and also several diseases, both bacterial and 

 fungous, they are not sufficient checks to prevent considerable injury. 



Control. — Pasturing hogs in fields considerably infested by white 

 grubs is a good practice, the hogs feeding on other insects they find in the 

 ground, as well. Poultry can be made use of in the same way, but this is 

 most effective when the ground is being cultivated. Rotation of crops 

 is also of value if used intelligently. Corn and clover are crops in which 

 the beetles will not lay eggs freely. Grain fields have many eggs laid in 

 them, but if followed by clover the grubs will do little damage. Fall 

 plowing before the grubs go down to pass the winter will destroy many of 

 them. This should be done as late before the grubs start down as possible. 

 The spring after beetles were abundant the year before, many small grubs 

 should be found in cultivating. In this case seed with small grain or 

 clover. If large grubs are abundant either in the fall or the following 

 spring, plant late if possible, as the grubs finish feeding before July in 

 most cases; or plow as soon after July 15 as possible, to break up and 

 destroy the pupae. Where beetles are stripping foliage, spraying with a 

 stomach poison, standard, or a little above standard strength, is a good 

 treatment where conditions are such as to make it practicable. 



