lice belong to the Order Anoplura and the members of this
small insect group show many adaptations for their specialised parasitic
life. They are wingless, have much reduced eyes and their mouth
parts are adapted for biting and sucking. The skin of a louse
is leathery and greyish, and the abdomen becomes much distended when
full of blood. Each leg ends in a claw which is adapted for gripping
hairs. Lice feed exclusively on blood and as they have to feed
twice a day if they are to remain in good condition they can only survive
for a few days in the absence of a host. A louse that is really
hungry may be so greedy when it does again find a host that it will
feed until it literally almost bursts. Lice are completely dependant
upon the special micro climate found near the surface of the skin.
If the temperature changes as, for example, when the host has a fever,
they will move away, and in former times it was considered a very bad
sign when lice left their host. Lice also move off very quickly
from a cold, dead person and this naturally increases the risk of infection
female louse lays about 10 eggs per day during it's month of life.
The eggs are quite large and a yellowish - white and so firmly attached
that it is practically impossible to remove them. After about
a week the egg is ready to hatch and the young louse inside inflates
itself with air, pushes off the top of the egg and crawls out.
The newly hatched louse starts to feed immediately and after about 8
days is ready to mate and lay eggs. A population of lice that is left
undisturbed can therefore increase at a fast rate.
are by no means a new problem, most mammals harbour their own special
species and there is no doubt that our primate ancestors also harboured
them. It is, in fact, probable that the louse now found on modern
man is the same or closely related to the species that infested early
man. In most periods of history lice have been regarded as something
that one lived with, and the job of delousing one another was an important
part of family life.
types of louse are adapted for living on man: the human louse, and the
crab louse. The human louse occurs in two forms, the body louse
and the head louse, and these are very similar to one another.
In fact they can only be distinguished with certainty by their habits.
The body louse is Pediculus humanus (var. corporis) and
the head louse is Pediculus humanus (var. capitis)