10 BULLETIN 535, U. S. DEPARTMENT OF AGRICULTURE. 
very numerous, the petiole is tunneled to the extent that it shrinks 
considerably and causes the leaf to wither and die at the tip and 
about the margins. When the larva is ready for pupation, it leaves 
the petiole and enters the ground. The exit holes, which soon collapse 
and appear as brown spots, are also characteristic of larval injury. 
When both larve and adults occur together, the former are the 
more injurious. The injury which the adults cause to the young 
shoots early in spring as they are breaking through the soil is pos- 
sibly more serious than subsequent injuries. 
That the larva may live in the roots of the plant has been clearly 
demonstrated since it was first reported to the senior author. A 
potted plant died and was left intact for about a month. When the 
pot was wanted for another experiment the soil was found to con- 
tain several larve and pupx. Only the shell of a root remained, the 
contents having been completely devoured by the larve. The pupz 
transformed to normal adults shortly afterward. This habit of de- 
scending to the roots is not very general, however, for it has never 
been observed while roots peeled for the shredder were being ex- 
amined. 
After leaving the plant the larva enters the soil to a depth of from 
one-eighth to one-fourth of an inch or even 3 inches. Here it re- 
mains for 4 or 5 days, when it becomes white and short and thick. 
In this form it is inactive. From 2 to 6 days, usually 3 or 4, inter- 
vene before pupation. 
The total larval period of an individual which was deposited as 
an egg on! May 1, and which was hatched about May 15, was 48 days 
(about May 15 to about July 6). Another. required 52 days; two 
others reqtiired about 57 days, two others 64 days, and two others 
66 days. 
The two larve which developed in 48 and 52 days, respectively, 
each remained 10 days in the pupal stage. Three other individuals 
also passed the pupal stage in 10 days, but one required 12 ~~ 
while three required from 12 to 13 days. 
On September 11, 1915, a few pupe in the cages had not yet trans- 
formed. April 17, 1915, the adults were already numerous about the 
ground where the shoots of horse-radish were just appearing, or 
about to appear. 
This flea-beetle, lke others of its kind, and like most leaf-beetles, 
hibernates in the adult stage. Careful search for pupe from time to 
time practically proves this. 
In Wisconsin only one generation appears annually. 
The total period of time from egg laying to adult ranges from 77 
days to about 90 days in the cases where complete records were 
obtained. Repeated attempts to obtain eggs from the adults of the 
current season failed. 
