Often, indeed, I find winged
forms upon the leaf-stem of a nasturtium, having come there evidently in
hopes of starting a new colony; but usually in a dead or dying
condition--the pungent juice seems to have poisoned them. So, too,
spinach and lettuce may be covered with blight, while the bitter
spurges, the woolly-leaved arabis, and the strong-scented thyme close by
are utterly untouched. Plants seem to have acquired all these devices,
such as close networks of hair upon the leaves, strong essences, bitter
or pungent juices, and poisonous principles, mainly as deterrents for
insect enemies, of which caterpillars and plant-lice are by far the most
destructive. It would be unpardonable, of course, to write about
honey-dew without mentioning tobacco; and I may add parenthetically that
aphides are determined anti-tobacconists, nicotine, in fact, being a
deadly poison to them. Smoking with tobacco, or sprinkling with
tobacco-water, are familiar modes of getting rid of the unwelcome
intruders in gardens. Doubtless this peculiar property of the tobacco
plant has been developed as a prophylactic against insect enemies: and
if so, we may perhaps owe the weed itself, as a smokable leaf, to the
little aphides. Granting this hypothetical connection, the name of
honey-dew would indeed be a peculiarly appropriate one. I may mention in
passing that tobacco is quite fatal to almost all insects, a fact which
I present gratuitously to the blowers of counterblasts, who are at
liberty to make whatever use they choose of it.
Pages:
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216