THE ARACHNIDA. 299 
its metamorphosis. What is said of its eggs? Describe the arrange- 
ment of the proboscis. What is said of the Musquitoes in various 
regions of the earth? What is said of the order Aphaniptera? What 
of the order Aptera ? 
CHAPTER XXX. 
THE ARACHNIDA. 
508. Tur second class of the Articulata is that of the 
Myriapoda, the Centipedes, § 388. This I will not dwell 
upon, but will pass directly to the third class, the Arach- 
nida. ‘This class was for a long time included among the 
Insects, and Spiders are very generally spoken of now, 
in common conversation, as belonging to that class; but 
the Arachnida differ from Insects in several important 
particulars. The head of Insects is distinct from the 
chest, but in the Arachnida the head and chest are united 
in one; and this is called the cephalo-thorax. Insects in 
their perfect state have but six legs, but the Arachnida 
have eight. The Arachnida have not the compound 
eyes of Insects. Again, the antennz of Insects are want- 
ing in the Arachnida. 
509. The Arachnida are carnivorous; but generally, 
instead of eating their prey, they suck the juices from 
their bodies. Many of them have a poison apparatus, 
by which they can destroy more readily those victims 
whose strength would otherwise be too much for them. 
They have mandibles and pincers very much like those 
of insects. In those which are parasitical—that is, those 
which dwell on other animals—the mouth has the form 
of a trunk or proboscis armed with a kind of lancet. The 
Scorpions have a curved and pointed instrument at the 
end of the tail, as seen in Fig. 233 (p. 300). They have 
large claws, like those of the Lobster, with which they 
seize their victims, and then pierce them with this curved 
sting, which is armed with poison from a gland. 
