CK12 Life Science

The arachnids are divided into eleven subgroups.Table(12.4) shows the four most familiar
subgroups, with a description of each.

Table 12.4:

Subgroup of Arach-

nid

Representative Or-

ganisms

Approximate Num-

ber of Species

Description

Araneae Spiders 40,000

Found all over

the world,

ranging from

tropics to the

Arctic, some

in extreme

environments;

All produce silk,

used for many

functions,

including trap-

ping insects in

webs, aiding

in climb-

ing, forming

smooth walls

for burrows,

producing

egg sacs, and

wrapping prey

Nearly all spiders

inject venom

to protect

themselves or

to kill prey;

only about 200

species have

bites that can

be harmful to

humans