Tlie Colorado Potato-Bcetla. 
369 
few spoonfuls of which are to be taken in cases where symptoms 
of poisoning show themselves.*' It is to be hoped that English 
farmers may have no occasion for resorting to so des])erate a 
remedy. Much discussion has taken place in America regarding 
the effect, on the soil and the tubers, of the inevitable wash- 
ing in of quantities of the poison ; some cultivators having 
asserted that peas planted in soil which had been mixed with 
the green had rotted immediately and failed to germinate, but 
Mr. Riley has proved by experiment that no harm is caused. 
He planted five rows of peas, using no green on the first, a little 
on the second, and increasing the amount on the others, so that 
on the fifth the peas had, in addition to that mixed with the 
soil, a covering of about one-eighth of an inch ; the peas all 
grew and bloomed without noticeable difference, and were finally 
eaten with impunity by a cow. There seems to be no doubt, 
however, that wherever the beetles are not in excessive num- 
bers, persevering hand-picking is sufficient to check their devas- 
tations. The best way to do this is to watch for their first 
appearance in spring and destroy them before they have time 
to pair and propagate their kind. 
The experience of a few years in the Western States has 
shown that the natural enemies of the beetle — insectivorous birds, 
and parasitic or predacious insects — are capable by themselves 
of checking the increase of the pest, and the fullest details are 
given by Riley and others regarding the forms and habits of 
these allies of the cultivator, so that when seen they may be 
treated as friends. It is a curious fact that for the first year or 
two of the appearance of the potato-beetle in any district, these 
vermin-killers seem not to find out the palatableness of their 
new prey ; but they gradually become accustomed to it, and 
afterwards increase in numbers in proportion to the increase of 
their victims. At first none of the domestic poultry, with the 
exception of ducks, would touch the insects, probably on account 
of the fluid exuded from the mouths of the beetles, which has 
a highly astringent taste, and an acrid property which causes a 
slight burning when it is applied to the skin. But afterwards 
fowis learned to feed upon them, and now when turned loose in the 
fields devour immense quantities. The rose-breasted grosbeak 
(Guiraca Ludoviciana) renders also great service by the number 
it destroys ; formerly a scarce bird in the West, it has become 
common, at least in the State of Iowa, since the invasion of the 
Doryphora. But the most effective destroyers are members of 
the insect class, particularly a small parasitic fly {Lydella Dory- 
phorce), from the eggs of which, laid in clusters on the neck of 
the larva of the beetle, maggots are soon hatched, which pene- 
trate the skin, and kill their prey by devouring the entrails. Six 
