U. S. DEPAETMEXT OF AGKI CULTURE. 
the majority of flea-beetles, this species does most harm to young 
plants, and, as an instance of its destructiveness, it has been reported 
to come in swarms, like black clouds, completely covering the plants. 
This species is not a periodical pest, like army worms and others, 
but it is more or less injurious year after year in the regions which 
it inhabits. It is, however, like most other flea-beetles, subject to 
considerable fluctuation in numbers for reasons which have not yet 
been entirely explained, but which are doubtless due to atmospheric 
conditions either at the time that the insect is breeding or when it 
is in hibernation. 
DESCRIPTION. 
BEETLE. 
The adult of the western cabbage flea-beetle (fig. 1) is shining 
metallic copper in color, measuring one-sixteenth of an inch or a little 
more in length. The body is elongate oval, 
much flattened. The antennae are slender and 
^ the same hi both sexes. The thighs of the 
hind legs- are strongly developed, fitting the 
insect for jumping, whence its common name 
jgi :5^ of "flea" or flea-beetle. 
~A | I L^ Following is the original description of 
<* A v Pliyllotreta pusilla (-5, 1 p. 302): 
Form. narrow, elongate, depressed, piceous, surface with 
\ iKiilfil^ i ^ distinct aeneous lustre. Antenna? slender, half as long as 
y- ^gypP^ *!& the body, piceous, joints 2-3 paler. Head scarcely visibly 
* punctate. Thorax less than twice as wide as long, widest 
Fig. l.-The western cabbage at ^^ sides arcuate a pex slightly narrower than base, 
flea-beatle (Phyllotreta pus- _. ' . r . °. J ' 
iWa):Adult highly magnified. dlsc conYex ' surtace shining, the punctures moderate, 
closely placed, but not convex. Elytra wider than the 
thorax, humeri obtuse, punctation coarser than that of the thorax, closely placed, 
very little finer near the apex, but less dense, surface shining. Body beneath and 
legs piceous, abdomen sparsely punctate. Length .06 — .08 inch; 1.5-2 mm. 
Male — Last ventral [segment] with a feeble triangular impression in the apex. 
Female. — Last ventral simple. 
The antennae are alike in both sexes and the joints 3 to 10 vary 
little hi length, although slightly broader externally. 
This species is very easily confounded with related forms of similar 
habits. Prominent among these is Pliyllotreta albionica Lee, which 
it resembles so nearly hi form, size, and color that the females can 
scarcely be separated. It is, however, more shining, the head is 
nearly smooth, and the thorax and elytra are less densely punctate. 
Moreover, PJi. albionica may easily be separated by the male antennas 
which have the fifth joint dilated. The female antenna? of the two 
species are almost identical. The color of pusilla is sometimes olive 
brown and inclined to black, but examination of a large series of 
properly preserved specimens does not show any material variation, 
1 Reference is made by number (italic) to " Literature cited,'' p. 21. 
