450 



Bulletin No. 116. [August, 



Whatever the length of life in the grub stage, all our most 

 abundant species of Lachnosterna begin to pupate in June or July 

 in central Illinois, and begin to change to the beetle in August or 

 September, remaining, with rare or doubtful individual exceptions, 

 under ground in this stage until the following March, April, or 

 May. They then emerge from their winter quarters, feed on the 

 leaves of various trees, and pair and lay their eggs in the earth in 

 June and July. An exception should perhaps be made, provisionally, 

 of L. tristis, concerning which my records are unusually imperfect, 

 agreeing, so far as they go, with those of the other species of our 

 list, but stopping short before the middle of June. That is, we have 

 an abundance of the beetles collected from the latter part of March 

 through April and May and into early June, most frequently, how- 

 ever, in May, but have no collections in any stage at any date later 

 than June 5. Four of our lots of tristis, collected in March and 

 April, were beetles taken from the earth, which must have trans- 

 formed the preceding summer or fall. 



Pupae of the above species have been taken by us from their 

 tmderground cells only in June, July, August, and September, and 

 the adult beetles have been found under ground in the cells where 

 they originated, in August, September, October, and November, and 

 again in April and early May. Adults of various species have been 

 seen pairing in May, and in one case in June, and eggs of seven of 

 these species — tristis being omitted — have been secured in June and 

 July, much the greater part of them in the former month. So far 

 as my rather scanty records go, the eggs may be exp,ected to hatch 

 from ten days to four weeks from the time of deposit. My dates 

 for the hatching of eggs of known species are, for inversa, June 23 

 and July 11 ; for fusca, June 27; for implicita, July 16, 21, and 24, 

 and August 7 ; and for hirticula, July 7. 



From this it will appear that white-grubs found in the earth 

 beyond the middle of September will not change to the beetle that 

 year, but, barring destruction by parasites and other fatal accidents, 

 may be expected to pass the winter as grubs and to continue in 

 that stage at least until the following June. This is a point of 

 special economic interest, since the owner of infested fields needs to 

 know whether the grubs in the ground during the latter part of the 

 season will continue there in dangerous numbers during the follow- 

 ing spring, or whether he may expect relief from their injuries by 

 reason of their change to the beetle. 



The data of my collections, when taken in the aggregate for 

 several years, give little indication of any fixed order of succession 



