Fleas
Fleas are a relatively small but distinct group of insects known as
the Siphonaptera. All fleas are parasitic as adults on warm-blooded animals
(mammals or birds) and most are adapted to living on one type of animal
(or close relations). Some species are able to feed on a range of hosts
but may only be able to breed when feeding on their primary host. A number
of species are important pests but the cat flea is by far the most common
flea found in domestic premises. The cat flea is usually found in association
with the domestic cat, but it is often found on dogs and will bite humans.
Fleas cannot jump higher than 6 inches.
The adults spend only some of their time on the host animal, usually
only to feed, the majority of the time is spent in the hosts bedding
or carpets from where they can climb or hop back onto the host when they
require a feed.
Life Cycle
Fleas have a distinct larval (or grub) phase and an intermediate pupae
stage between the larva and adult. The life cycle is therefore very different
to the bed bugs and lice whose young are similar in appearance and habit
to the adult and are called nymphs. The female flea may lay as many as
25 eggs per day with a total of about 800-1000 eggs during a lifetime,
which may last over a year. The eggs may be laid in the host’s
bed or lodge in the fur before dropping off onto the floor. They hatch
after about 5 days and the small white larvae which emerge feed on organic
debris and on adult flea faeces, rich in partly digested blood After
about three weeks, during which time they molt twice, the fully grown
larvae spin a silk cocoon covered in debris in which to pupate. They
moult after three days and change into the pupae stage. A gradual transformation
now takes place and after about 2 weeks the adult emerges from the pupa.
It does not immediately leave the cocoon, however, unless stimulated
by vibrations, which indicate the presence of a host. It can remain in
this ‘waiting state’ for up to 1 year. Thus, a heavy flea
infestation may appear in a building room, which has been unoccupied
for some time. In good conditions in heated premises the life cycle takes
about 4-6 weeks from egg too adult but longer at lower temperatures.
Once they have emerged from the pupa, adults normally live for 2-4 months
if feeding regularly. They can survive over a year at lower temperatures.
Both males and females require blood for nutrition and feed on nothing
else. The female also requires blood from her preferred host in order
to lay viable eggs, so an infestation where no domestic animals are present
will not breed but will still need treatment as the fleas will feed of
humans in the absence of domestic animals. Fleas will often prefer women & children
to men, no one knows why.
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Where conditions are favourable fleas will eat more than they need excreting
more semi-digested blood than usual for their grubs to feed on. This
ensures that the population expands when conditions are right.
It is often the case that a flea infestation will go unnoticed by the human inhabitants
until the removal of the host animal, after which the fleas are forced to look
for alternative food, i.e. humans. It is common that previously empty houses
or houses where a cat was living will have a flea problem once the new occupiers
move in. The original owners may have not realized there was a problem, as the
fleas would have been feeding on the animal leaving the people alone.
The eggs of the flea are comparatively large, 0.5 mm in length and oval or round
in shape, pearly white in colour and are sticky which attracts debris from the
surrounding habitat, thus camouflaging their appearance.
For every flea found on the host there will probably be a hundred or so in the
bedding (if there is any as most cats are allowed to sleep any where in the house)
and carpets, hence the effectiveness of insecticidal collars on the animal without
a full treatment is very limited. The cat flea commonly causes domestic infestations
in Britain.
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