58 THE EEPORT OF THE No. 36 



are continuing to be, accumulated through the co-operation of entomologists in 

 Canada and the United States. 



As might be expected for an insect having so widespread distribution and 

 involving a life cycle of three years, the white grubs have several definite destruc- 

 tive broods. The important brood which occurs more or less continuously through 

 the northern states from South Dakota to the Atlantic coast and in southern 

 Ontario is present in the beetle stage every three years, 1917 being the last year 

 the May-beetles were numerous. The year following the flight of beetles might 

 be termed the "grub year " since the grubs are then in their most destructive stage. 

 The important brood under discussion evidently began in an accumulative way 

 some score of years ago. By. 1909 and especially in 1912, they had become very 

 abundant and destructive over a considerable area. In 1915 the grubs were again 

 as abundant, or more so, as in 1912 but the damage was much less evident because 

 the season was wet, which greatly assisted the corn and pastures to overcome some 

 of the destructive work of the grubs. The past season (1918) grubs were again 

 abundant, although less numerous than for several years past, but fortunately the 

 conditions have been against the pests and comparatively small damage resulted. 

 Parasites, predaceous enemies, and diseases have played a part in this result but 

 certain climatic conditions are in a large measure responsible. In the spring of 

 1917 May -beetles were apparently as numerous in the soil as in any previous 

 beetle year but the season was late and cold and the beetles came to trees in small 

 numbers until quite late. Only a small percentage of the normal number of eggs 

 were laid and most of these late in the season. As a consequence the grubs were 

 abnormally small when cold weather set in, many of them too small to pass the 

 winter successfully. This year the comparatively few grubs were small when the 

 ground warmed up and they did not reach their destructive developmental stage 

 until late in the year. From general observations it appears certain that the years 

 of maximum abundance are passed and that we may expect fewer grubs of this 

 particular brood for a number of years before conditions will again favor their 

 enormous increase. 



The principal methods of combatting white grubs are rotations and utilization 

 of hogs and poultry. In white grub districts rotations should be arranged so that 

 corn and other susceptible crops will not be planted on ground likely to contain 

 grubs the year of their abundance, or better, the use of clover in the rotation, 

 the clover to be followed by corn, since the beetles do not deposit many eggs in 

 ground covered with a stand of clover during the May-beetle flight. The value of 

 hogs to clear land of grubs: has been repeatedly demonstrated. Other practices, 

 such as fall plowing and the collection of May-beetles and grubs are only partially 

 successful, but are good practices when supplemented by the measures already 

 mentioned. 



I have purposely discussed several of the more important insects of cereal 

 and forage crops which have occupied our attention the past year or two. It is 

 usual and to be expected that the economic entomologist spends much of his time 

 with insects which appear in conspicuous numbers. There are however, hordes of 

 insects of less importance which nevertheless are always present and which con- 

 stitute a continuous drain on our crops but because of the inconspicuousness and 

 gradualness of the losses they are not recognized seriously. Many of these incon- 

 spicuous insects are taking a heavy toll, and I believe we are coming to a time 

 when they will be given their just consideration and it might be added, their just 

 deserts. 



