416 
Observations on the various Insects 
these checks are sufficient to keep this tribe of insects under 
without the intervention of man, and by })ushing persecution too 
far, it is not improbable that "in avoiding Scylla we might fall on 
Charybdis, ' for if the Humble-bees could be extirpated, in all 
probability the beans would not be so prolific, and by the de- 
struction of some flowers it is almost certain that those which 
escape form larger and finer pods and seeds. These are fit 
subjects for the cultivator to investigate, and into his hands we 
consign the subject. Hive -bees have been accused also of assist- 
ing in puncturing the flowers, but Mr. Darwin thinks they only 
participate in taking advantage of the labours of their bustling 
neighbours, as they do not exhibit the adroitness which the 
Humble-bees do in detecting the hidden treasure. 
Aphides, or Plant-lice. 
Another tribe of insects we have to record, which destroy or 
injure the Peas and Beans in the field, are the Aphides, from 
which no crop is entirely free ; the former of these plants are 
often smothered with the Lice," or '' Greea Dolphin," as they 
are termed, and the latter seldom escape from the attacks of 
another species : these, from their sooty colour, have received 
the appellation of Black-fly, Black Dolphin, or Collier. Like 
all the insects of this family, of which we have already described 
many, their appearance is very sudden, and their increase so pro- 
digious, that crops suffer severely from their visits. In 1833 the 
Beans were almost totally destroyed by them in Yorkshire. In 
1841 they were abundant in my garden near the Regent's Park ; 
but in 1842 I never saw one on the spot, yet the Beans around 
Sandgate in the same year were very much injured by them. On 
the 5th of last June I could only find apterous specimens (fig. 
20, and 21 highly magnified) on the broad-bean tops, but on the 
11th I detected some winged specimens (fig. 22, the cross lines 
show the natural size), and the Beans in the jiotato rows were 
smothered with them, whilst those in a separate bed were free, 
and by topping them the crop escaped. 
Dickson says, " In such summers as are dry, beans are fre- 
quently liable to be much injured by the attacks of the Black-fly, 
or what is often termed the Dolphin, the whole field in particular 
cases being in danger of being destroyed in the course of a few 
days. In order to prevent this mischief it is the practice in some 
places to cut off the tops by means of a scythe or other sharp 
implement, as it is mostly on the tops of the plants that the 
insect first appears. When this method is adopted it should be 
performed on the very first appearance of the fly, otherwise little 
benefit can be produced ; as, perhaps, by removing the first insects 
that show themselves, their propagation may in some degree be 
