et FOr. Me Ses ae Oe) Sy eee 5 ee as Sa ahs 20 
106 
vember to a depth beneath the surface varying according to the severity 
of the winter weather, and coming up again within reach of food com- 
monly some time in Mareh or early April. 
‘The time and place of hibernation have their especial economic in- 
terest, since while in their usual winter quarters the white grubs are 
far beyond the reach of any agricultural operations. ‘The distance to 
which they retreat in this lat itude is about a foot and a half, if I may 
judge from a single observation made November 29, 1886, in a badly 
infested field of wheat in Sangamon county, Illinois. Here, around the 
margins of denuded patehes,—the ground being frozen some four inches 
lee ‘p,—the white grubs were found repeatedly in numbers averaging 
four or five to the square foot at a depth varying from a foot and a 
half to two feet. In 1890 they had already come up, in the pastures, 
from their winter quarters by the 24th of March; were still at the 
surface in their usual number during the latter part of October; and 
had not wholly withdrawn by November 25—although at this late date 
most had gone beyond the reach of the plow. Notwithstanding this 
well-marked habit of retreat at the approach of winter, they occa- 
sionally lnger at the surface and hibernate at a depth scarcely greater 
than that at which they are to be found during the summer season. 
Pupation and Formation of the Beetle—The full-grown white 
grubs, presumed to be two years old according to the prec eding section, 
ial live an active life in the earth, feeding freely from March to June 
r July, during which months they change to the pupa a few inches 
Wey ground, in oval cells made by the grub by turning about in the 
earth. In this smooth-walled chamber the cutieular remnant of the 
last moult will be found enclosed with the pupa—that is, the crust of 
the head of the grub and shriveled fragments of its last skin. Our 
first date for this pupal transformation of L. inversa is June 13, 1889, 
but Professor Perkins notes* the pupation of two larvae out of several 
hundred early in May.t In this chamber they he until August or Sep- 
tember, when they change to the June beetle, fusca and gibbosa as early - 
as August 11, and others—at least individuals of implicita, for ex- 
ample—not before September 17%. A small percentage of the adults 
thus formed late in the summer and in early fall, may escape from 
the earth before the winter opens, but this is relatively a rare oceur- 
rence, the great mass of the generation continuing through the winter 
in the pupal cells within which they originated. ‘They are to be found 
in winter from no more than two or three inches to about ten inches be- 
meath the surface. Hence they escape in spring, as already described, 
pairing and laying their eggs for the generation following. 
From the foregoing it will be seen that the white grubs of the 
genus Lachnosterna hibernate in two stages only, those of larva and 
imago, the grubs themselves representing at least two generations. 
* PWifth Ann. Rep. Vt. Agr. Exper. Station (1891), p. 148. 
+ From the fact that the grub of Cyclocephala pupates in May in Tllinois, I 
surmise that the above-mentioned larvez belong to this genus, and were not dis- 
tinguished from the Lachnosterna larve among which they occurred, 
+ Por the full particulars upon which the foregoing statement is based, see 
Seventeenth Rep. State Ent. Ill, pp. 31-38. To the data there tabulated, I may add 
the following items noted in 1891: Grubs of L. fusea collected in corn fields near 
Champaign, April 16 and 17 and May 2, had begun to pupate July 18; and those 
of L. rugosa, taken at the same times and places, had formed two pup at this last 
date just mentioned, 
