234 
Destructive Insects and Utilitij of Birds. 
Some chemists have succeeded in extracting from them a good 
brown colour and a good Prussian blue ; much oil, too, can be 
got out of them, 16 measures of cockchafers giving 6 measures 
of oil. A clear gas and a fair sort of cart-grease may also be 
manufactured from them ; whilst cooks even turn them into a 
nourishing and savoury soup, or a sweetmeat for dessert. 
All this is doubtless very well in its way, but if we do not 
steadily persevere in our labour of limiting, to the utmost of our 
power, the number of cockchafers, they would in the long run 
ravage so many lands that neither hens, cows, cooks, nor chemists 
could by any possible means exist. Other destructive beetles 
are the Acanthopoda, the Astijnomus (sdili, the Anthonomus, the 
Bostriclius ty])ographus, which in 1780 and the following years 
destroyed more than a million of fir-trees in the Hartz Mountains 
and in Switzerland, and more recently committed other awful 
depredations ; and lastly the Hydroyhilus atei, a very dangerous 
insect for preserved fishponds. Several species of butterflies, 
otherwise so innocent, belong when in the caterpillar state to the 
class of pernicious articulated animals ; the principal of these 
are the Bombyx processionea, the Phalena bomhyx, the Pieris, 
the Lasiocampa, the Phalena, the Neustria, and the Tinea. As 
for the other sorts of inferior insects, such as the ChyllofaJpa, the 
Aphis, the grasshopper, the ant, different species of the gadfly, 
wasps, flies, worms, and snails, it is almost needless to speak of 
them ; they are but too well known as plagues. The Acridium 
migratorium has already penetrated into Southern Switzerland, 
and we are forced to come to the conclusion, from observations 
carefully made on different spots, that the number of destructive 
insects in general is gradually augmenting. This arises evi- 
dently from the diminution of insectivorous birds, which is in 
exact proportion to the increase of insects ; and if we look into 
the causes of this diminution we shall find more than one, both 
in this and other lands. Generally speaking, the progressive 
cultivation of the earth is not very favourable to animals living 
in freedom. It has driven the fallow deer from our woods ; the 
elk, the lynx, the wolf, the bear, the ibex, from our mountains ; 
tke beaver from our rivers. But it has been especially hostile to 
birds ; the hospitable thickets diminish yearly ; man forces 
onward the limits of his domain ; he masters the as yet unculti- 
vated soil, and draws from it rich harvests. Large tracts of 
woodland are cleared to supply the wants of an increasing 
population and the heavy demands of industry. The large trees 
formerly left standing in the midst of a field, in which number- 
less small animals found a refuge, are made away with, or 
replaced sometimes by the small fruit-tree. Long rows of hedges, 
the hidingplace of a whole host of birds, meet with the like fate; 
