82 SOME INSECTS INJURIOUS TO TRUCK CROPS. 
H. Carpenter as a cabbage pest in an article in which the larva is 
described and illustrated in detail. As to its biology Mr. Carpenter a 
reaches the conclusion that the female beetle lays her eggs on the 
underground part of the stem and that the young larva burrows 
through into the interior and feeds in the central tissue of the stem 
and taproot until mature. The papal stage lasts about three weeks 
and is passed in an earthen cell just beneath the surface. The 
natural larval food plant is evidently a wild crucifer. 
LOCAL CONDITIONS AND NATURAL INFLUENCES. 
Inquiry was made of Mr. Eder during his visit to Washington, 
D. C., in December, 1908, as to the local conditions in the infested 
area. From what was learned through him it would appear that the 
insect's occurrence in such great numbers in the hopyards of British 
Columbia was due to the equable temperature and to the humidity, 
which keeps the soil practically always sufficiently moist for the oper- 
ations of the larva? feeding beneath the surface. 
There can be no doubt, from the writer's observations of our east- 
ern flea-beetles, that these are largely held in check, especially in 
regions like the District of Columbia, by the extremely dry heat of 
midsummer. At the time that the flea-beetles are developing as 
larvae or undergoing their transformation the ground is nearly baked 
by the heat during the da}^ and softened only by dews at night. The 
conditions are very different in British Columbia, and there are, 
moreover, no other natural causes known which might assist in de- 
pleting the numbers of the little pest. 
Among natural agencies only a single species of insect has as yet 
been discovered preying upon this flea-beetle, a hymenopterous para- 
site which was known to Fitch - and which he mentions as a " Chal- 
cidian." It is evidently a species of Perilitus, probably the same 
species, schwarzii Ashm.(?), as has been encountered by the writer 
on other species of flea -beetles of the genera Epitrix and Phyllotreta. 
It develops within the body of the adult or beetle. It is not known 
if this species occurs also in the Pacific region. If not, it might be 
possible to introduce it. 
Fitch's observations and conclusions are interesting, since we have 
no reason to doubt his theory. Briefly he observed on June 1, 1863, 
two flea-beetles pairing on a leaf of rhubarb. Presently a parasite 
alighted near them. It darted upon the back of the female, appear- 
ing to be inserting its sting in the tip of her body, whereupon she 
gave a leap and they both disappeared among the foliage. Fitch 
conjectured that the " chalcidian " was an egg-parasite of the flea- 
a Journal of Economic Biology, Vol. I, pp. 152-156, PL XI. London, England, 
November, 1906. 
