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LETTERS ON ENTOMOLOGY. 35 
as the race of flies, or musca, strictly so called, 
and gnats, with a great variety of others. Aptera 
is the last order, and comprises wingless insects. 
It consists, according to Linnaeus, of the crab 
and lobster tribe, of spiders, scorpions, centi- 
pedes, monoculi, mites, and many others. 
Insects pass through four states : the egg, the 
larva, the pupa, or chrysalis, and the imago, or 
perfect state. You need not be told what the 
first is. The second, is when they first leave the 
egg and are like soft worms. Linnaeus calls this 
the larva state, and we have given it different 
names according to the species, as caterpillars, 
which are the larvae of the butterfly or moth ; 
maggots or grubs, which belong to the fly and 
beetle tribes, &c. In this state, during which 
they eat voraciously, and cast their skins several 
times, they remain different periods, some a few 
days, and others years. They cease eating, and 
fix themselves in a secure place, their skin sepa- 
rates, and discloses an oblong body, and thus 
they have attained the third stage of their ex- 
istence, which is called the pupa or chrysalis. 
It is not a general rule that they do not eat in 
this state, for a considerable number, as locusts, 
cockroaches, bugs, spiders, &c. not only greatly 
