1920 ENTOMOLOGICAL SOCIETY 



81 



SOME NOTES ON THE LIFE HISTOliV OF OUR COMMON JUNE 



BEETLES. 



H. F. Hudson, Dominion' Entomological L.\boi;atoi:y. Sti!Athi!oy. 



The white grub, the iniiuature form of the May or June beetle, is one of the 

 most important and most ijijurious of soil-infesting insects, and one of the hardest 

 to control, on the sand and sandy loam soils of Western Ontario. Thev nia\ 

 occur occasionally in clay soils, but I have never observed ,or known of any in- 

 jury by these insects on the heavier types of soil. Since I'Jli. observations on 

 the life history of these important insects have been under observation, and tbougb 

 I he work has had a chequered career, we have been able to breed out from lhe egg, 

 the complete life history of three species. So far as our collection of beetles is 

 loncerned, and that involves many thousands, we have in Middlesex County seven 

 distinct species, but probably only four are really common, although no extensive 

 collections of beetles have been made outside of Caradoc Township. This is some- 

 what to be regretted as it does not give us a proper idea of the distribution of the 

 different species. The seven species known to exist in Middlesex County are 

 L. fusca. L. rugosa, L. duhia, L. gibbosa, L. nmrginalis, L. Uicifi. and L. inr('.ii<a. 

 The three species raised from the egg are L. dubia. L. rugosa, L. gibbosa. The year 

 1914 was an excellent year for the collection of beetles, thousands were present, 

 and ash, willow and butternut trees, were freely stripped of their foliage, while 

 the early blossoms of cherry trees were freely fed on by the beetles. Coming early 

 in May, the time of appearance being governed largely by temperature the beetles 

 soon pair, frequently before they have eaten anything, but from observation eggs 

 are not laid until from two to three weeks after fertilization. The female pairs 

 frequently, at least 1 have seen the same pairs frequently in copula in theii' breed- 

 ing cages. Pairs taken in copula May 16tli, 1914, did not lay eggs until Jam 

 IGth, but this was possibly due to my negligence in omitting to place a piece of 

 sod in the breeding cage for the female to oviposit in. 1 noticed the day after 

 the sod was introduced eggs were laid. The eggs are small, oval, of a pearly 

 white lustre, each deposited singly in a ball of earth from 2 in. to 6 in. below the 

 surface. After having been laid several days the eggs increase slightly in size, 

 probably due to the absorption of moisture, become spherical in form and change 

 to a reddish colour just prior to hatching. Our brooding cage records show that 

 eggs hatch in from ten days to three weeks with an average of two weeks. This 

 is somewhat difficult to gauge as we have noticed breaking open the little balls 

 of earth to ascertain the egg yield, has undoubtedly a detrimental elfect on the 

 vitality of the young grub. The work of 1914 was practically, concluded owing 

 to the war, and although an assistant was procured in 1915, the results of the 

 previous year's work amounted to nil. With the api)ointment of Mr. H. G. Craw- 

 ford in the spring of 191G the work obtained a new lease of life and much of the 

 success of this work is duo to his untiring and unceasing efforts. Starting with 

 two species the results of that work were carried through to completion in the 

 fall of 1918. On my return in. the spring of 1917 the work was enlarged and 

 additional species studied. We have now definitely ascertained the life historv 

 of L. gibbosa, L. rugosa. and //. dubia to bo at least three years and in some cases 

 it may be four. 



The grubs feed most ravenously during the second and third year of their 

 growth, prepare to pupate the latter part of July or early August of the third year 



6 E.S, 



