370 
The Colorado Potato-Beetle. 
species of "ladybirds" (^Coccinellce) also destroy vast numbers 
— the ladybird beetles themselves and their larvae both eating 
the Doryphora grubs on the plants. Besides these, several pre- 
dacious two-winged flies (^Asilus), beetles {Harpalus, Calosoma, 
Lcbia, Brachinus, &c.), wasps and true bugs (^Hemiptcrd), have 
been found preying upon the beetles or their larva». To the 
combined effect of the increased number of these natural 
enemies and the use of the Paris green it is said the ravages of 
the potato-beetle in the States first affected have lately much 
diminished, and the pest no longer inspires the dread it did 
formerly. 
The all-important question for the agricultural interest and 
the public of the British Islands is, What are the chances of the 
arrival and acclimatisation of this dangerous insect in this 
country ? The neighbouring States of the Continent have taken 
alarm, and their Governments, after obtaining the advice of 
scientific bodies, have, as already stated, placed the importation 
of American potatoes under close restrictions or prohibited it 
altogether. But the persons best qualified to form an opinion, 
the skilled entomologists of those countries, are by no means 
unanimous in believing even in the possibility of its establishing 
itself in Western Europe. Strictly analogous cases of insect 
migration from which to judge are wanting. In the first place, 
no single instance is known of a native American beetle becom- 
ing acclimatized in Europe. We have a striking case of the 
establishment in Britain of a troublesome weed from North 
America, the canal plant (^AnacJiaris alsinastmm), which in an 
incredibly short space of time propagated itself throughout the 
country in all places suited to its habits ; but no similar inva- 
sion by an insect species can be cited. The nearest approach 
to such a case is that of the vine destroyer (^Pliylloxera vastatrix), 
which has caused such havoc in French vineyards, and which 
Mr. Riley has proved to be an American insect, introduced 
with American varieties of grape-vine into France. But it is 
objected that this insect (an almost microscopic creature allied 
to the plant-lice) is too different in organization and habits 
from the highly organized potato-beetle to be quoted as an 
example. The PlnjUoxcra is a parasite, with all the tenacity of 
life and indestructibility of its class, and as such more liable 
than a freer type of insect, like the Duryphord, to be introduced 
anywhere with the plant to which it is inseparably attached. 
This insect is, however, the nearest analogous case we have to 
guide us. Reverse cases, that is, cases of the introduction and 
spread of European species in North America, many of them 
proving there destructive pests, are numerous enough. Thus 
the common English cabbage-butterfly {^Pieris rapcc) introduced 
