IN THE PHYSICAL SCIENCES. 
40 i 
mies. Now, to do this with the greatest effect, we must watch 
them through all their changes. There may, probably, be many 
persons ignorant that most insects pass through four stages of 
existence (of which the silk-worm affords a familial instance), 
1 st, the egg ; 2 dly, the caterpillar ; 3 dly. the chrysalis; and, 
4 thly, the butterfly or imago. It is in the second stage that in¬ 
sects generally do the most mischief. In the egg and the chry¬ 
salis they do none ; and in the imago, some do, and some do not. 
Though we are all familiar with the insect in the shape in which 
its ravages compel our attention, we are frequently unconscious 
of its identity under other shapes. Though our last year’s crop 
was destroyed by the wireworm, we should probably pass by a 
swarm of the parent beetle, the Elater Segetis, without being 
aware of the relationship; and in the same manner we look on 
the cockchafer, without suspecting that its issue is the grub which 
eats the roots of the grass. 
The follies committed for want of a little knowledge of ento¬ 
mology are well illustrated by Messrs. Kirby and Spence :— 
“ In Germany, the gardeners and country people with great in¬ 
dustry gather whole basketsful of the destructive cabbage-moth 
(Noctua Brassicce), and then bury them, which is just as if they 
should endeavour to kill a crab by covering it with water—for 
many of them being full grown, and ready to pass into their next 
state, which theydourder ground; instead of destroying them 
by this manoeuvre, their appearing again the following year in 
greater numbers is actually facilitated. Yet this plan, applied 
to our common cabbage-caterpillar, which does not go under 
ground, would succeed.” 
The process of destroying noxious insects by attacking them 
in their early stages is not new in this country. P. Musgrave 
collected the chrysalids in the spring, so as to become acquainted 
with them, and then employed peopfe to catch and kill the moths 
and butterflies. If you catch 200 in a day, you destroy 10,000 
eggs, which w'ould give 120,000 in a fortnight. Might not boys 
and girls be well employed in doing this ? They have all the 
organ of destructiveness. 
In short, it is abundantly evident, that if we knew them in all 
their changes, and know where they are concealed in autumn, 
winter, and spring, we might exterminate those multitudes which 
are now as the sands which are upon the sea shore. And if not 
all the knowledge required be yet in our possession, a great deal 
is, and might be easily imparted to the young farmer, if we could 
catch him in his chrysalis state ; and what little is still wanting 
would soon be accumulated, when we had set so many keen and 
interested eyes to observe: a fly could scarcely move but they 
would be watching him. 
