Cattle suffer both from lice and from ticks. Sheep and goats breed
ticks, but do not breed lice. Pigs breed lice large and hard. In
dogs are found the flea peculiar to the animal, the Cynoroestes. In
all animals that are subject to lice, the latter originate from the
animals themselves. Moreover, in animals that bathe at all, lice are
more than usually abundant when they change the water in which they
bathe.

In the sea, lice are found on fishes, but they are generated not
out of the fish but out of slime; and they resemble multipedal
wood-lice, only that their tail is flat. Sea-lice are uniform in shape
and universal in locality, and are particularly numerous on the body
of the red mullet. And all these insects are multipedal and devoid
of blood.

The parasite that feeds on the tunny is found in the region of
the fins; it resembles a scorpion, and is about the size of a
spider. In the seas between Cyrene and Egypt there is a fish that
attends on the dolphin, which is called the 'dolphin's louse'. This
fish gets exceedingly fat from enjoying an abundance of food while the
dolphin is out in pursuit of its prey.