532 INJURIOUS AND BENEFICIAL INSECTS. 
Lockwood remarks that “when collecting the larvæ in May, I 
often observed in the same places grubs of the Cotalpa of at least 
four distinct ages, each representing a year in the life of the 
insect, judging from Renny’s figures of the larvae of the English 
cockchafer, or dor beetle (Melolontha vulgaris). But the cock- 
chafer becomes an imago in January or February, and comes 
forth into active life in May, just four years from the deposit of 
the egg. Supposing our Cotalpa to take on the imago form in au- 
tumn, and to spend its life from that time to the next May in the 
ground, it would be five years old when it makes its début as an 
arboreal insect.” It is possible that Dr. Lockwood may be in 
error regarding the age of this beetle, as M. T. Reiset says in 
France this insect is three years in arriving at its perfect beetle 
state. The following remarks on the habits of the European 
chafer may aid observers in this country in studying the habits of 
our native species. M. Reiset says (see “Cosmos” as translated 
in the Amertcan Narura.isr,” vol. ii, p. 209) “that this beetle 
in the spring of 1865 defoliated the oaks and other trees, while 
immense numbers of their larve in the succeeding year, 1866, 
devoured to a fearful extent the roots of garden vegetables, etc., 
at a loss to the department of the lower Seine of over five millions 
of dollars. This insect is three years in arriving at its perfect 
beetle state. The larve, hatched from eggs laid by the beetles 
which appeared in such numbers in 1865, passed a second winter, 
that of 1867, at a mean depth in the soil of forty one-hundredths 
of a metre, or nearly afoot and a half. The thermometer placed 
in the ground (which was covered with snow) at this mean depth, 
never rose to thirty-two degrees F. as minimum. Thus the larve 
survived after being perfectly frozen (probably most subterranean 
larvee are thus frozen, and thaw out in the spring at the approach 
of warm weather). In June, 1867, the grubs having become fu 
fed, made their way upwards to a mean distance of about thirteen 
inches below the surface, where, in less than two months, they all 
changed to the pupa state, and in October and November the per- 
fect beetle appeared. The beetles, however, hibernate, remaining 
below the surface for a period of five or six months and appearing 
in April and May. The immature larve, warned by the approach- 
ing cold, began to migrate deep down in the soil in October, when 
the temperature of the earth was ten degrees above zero. = 
soon as the snow melted they gradually rose towards the surface. 
