Overview
Siphonaptera, commonly known as fleas, are parasitic insects that reside on their
hosts for as long as they can. Fleas only preside on mammals or birds
as they depend on either feathers or fur for protection. The fleas
will feed on their host using a long and slender, piercing mouth to
suck the blood of their hosts. Although some species can only reside
on specific hosts, most species of fleas are can move from host to
host. Morphologically most fleas are less than 5mm in length and are
laterally flattened. The shape of their bodies, being tall and skinny
instead of short and flat, helps them travel between fur and feathers
with relative ease. On their hind legs, fleas have enlarged coxae.
These allow fleas to jump a distance of a foot or more which is around
50 times their body length (Milne). Interestingly, fleas do not just
jump straight up in the air. As they are jumping, fleas will do a
complete somersault in the air (Urquhart). Eyesight is a sense which
is not particularly important to fleas. Most species have only minute
compound eyes, while some species have no eyes at all. Instead fleas
depend more on the sense of feeling to know when a perspective host is
near (Milne).
When female fleas lay eggs, they typically lay their eggs in the dirt or
on the ground, however, there are species that will directly lay their
eggs on the hair and feathers of their hosts. As the eggs hatch, the
larvae will feed on small pieces of organic matter such as dust. After
ample feeding, fleas will then pupate in silken cocoons. This stage of
their life can last anywhere from a few days up to a couple of months. In
many cases, the pupae will wait in their cocoons until they feel
vibrations emanating from possible hosts. In time, a full-grown adult flea
will emerge from its cocoon.
"Fleas (order Siphonaptera) are one of
the major groups of blood-sucking
insects. They belong to
holometabolic insects.
Holometabolism is a feature
characteristic also of Diptera,
Lepidoptera, etc. Fleas form a
separate well differentiated order,
although phylogenetically they are
regarded to be closer to Diptera and
Mecoptera. At present approximately
2000 species and subspecies of fleas
are known.
"Adult fleas are obligatory
hematophages parasitising
warm-blooded animals - mammals
and birds. Wormlike free-living legless
flea larva develops in the litter of
host's nest. The majority of fleas are
periodically attacking burrow or
nest-dwelling parasites, capable of long time to present in hostıs fur, unlike free blood-suckers,
such as, for example, Diptera or some bugs."-- (Zoological Institute of the Russian Academy of Sciences)
Identification
"The head capsule of fleas is very modified. It is high, narrow and cuneate. The
propleurosternum covers the head from below to the peristomal aperture, as result of which it
is immobile.
"The antennae of fleas are in antennal fossae. The antennal fossa divide the head into anterior
and posterior parts.
"The thorax consists of three modified segments. They are luck wings, but have long legs. The
hind legs are the principal jumping organs.
The abdomen of the adult flea includes 10 segments.
"The genital apparatus of male fleas consists of the aedeagus, modified tergites and sternites
of the 8th and 9th abdominal segments and claspers. The aedeagus and claspers derive from
primary phallic lobe (Snodgrass, 1946, 1957; Gunther, 1961). The modified tergites and
sternites of flea's belong to abdominal segments 7-9. More than 50 terms are used to describe
the structures of the genitalia. The complexity of the aedeagual structure is caused by the
separation of its internal duct (endophallus) into a number of complex sclerites. In addition,
the eternal walls of mesomeres form the apodeme, fulcrum, and palliolum of the aedeagus."-- (Zoological Institute of the Russian Academy of Sciences)
Geographic distribution
"The world fauna of the order Siphonaptera comprises 2000 species and 550 subspecies
belonging to 18 families and 4 infraorders. a great number of endemic species and genera are
distributed in East-Asian, Central-Asian, West-American, Patagonian, Papuan (New Guinean),
and East-African zoogeographical subregions. It is possible that forest foothills with
temperate and subtropical climate present the most favorable conditions for the fleas.
"The infraorder Pulicomorpha is characterized by more or less relations between the faunas of
Africa and Asia, Asia and South America.
"The existence of the Antarctic bridge in the Southern hemisphere and the Beringian bridge in
the Northern hemisphere had the most significant influence on the distribution of the
infraorders Pygiopsyllomorpha, Hystrichopsyllomorpha, and Ceratophyllomorpha."-- (Zoological Institute of the Russian Academy of Sciences)
Natural history
When female fleas lay eggs, they typically lay their eggs in the dirt
or on the ground, however, there are species that will directly lay
their eggs on the hair and feathers of their hosts. As the eggs
hatch, the larvae will either feed on small pieces of organic matter
such as dust (Urquhart) or cling to their host using small hooklike
appendages at the end of their abdomens. After ample feeding, fleas
will then pupate in silken cocoons. This stage of their life can last
anywhere from a few days up to a couple of months. In many cases, the
pupae will wait in their cocoons until they feel vibrations emanating
from possible hosts. In time, a full-grown adult flea will emerge from
its cocoon (Milne).
There are 16 separate families of Siphonaptera. However, it is hard
to put an estimate on the number of species in the order.
Morphologically, flea species don't vary that much from each other.
Coupled with the fact that fleas are already small, it makes
classifying them very difficult (Urquhart). Although some sources
say that there are around 3,000 species, it is probably more accurate
to estimate that there are over 16,000. It is normal for species of
Siphonaptera to be named after the host on which they are often found.
The family Pulicidae contains the species of fleas which humans will
typically come in contact with. Some of the species in the family are
the Cat Flea, the Dog Flea, the Oriental Rat Flea, and even the human
flea (Milne).
Fleas are also known to be the agents responsible for carrying and
transferring the bubonic plague from rats to people, which was
ultimately responsible for the death of nearly half of the population
of Europe during the Middle Ages.
"Fleas are obligatory blood feeders parasitizing warm-blooded invertebrates. More than 94% of
known species are parasites of the mammals and only about 5% of them occur on birds.
"The fleas have 4 phases of development - the egg, the free-living larva, the exarate pupa and
the imago.
"The larvae is wormlike, legless and eyeless with biting mouth parts. The larvae undergoes 3
instars. Prior to pupation it empties the alimentary canal, and spin a silken cocoon.
"The majority of fleas are closely associated with the host's home (nest, burrow etc),
attacking the host for feeding."-- (Zoological Institute of the Russian Academy of Sciences)
"Fleas pass through a complete life cycle consisting of egg, larva, pupa and adult. A typical flea
population consists of 50 percent eggs, 35 percent larvae, 10 percent pupae and 5 percent adults.
Completion of the life cycle from egg to adult varies from two weeks to eight months depending on the
temperature, humidity, food, and species. Normally after a blood meal, the female flea lays about 15 to
20 eggs per day up to 600 in a lifetime usually on the host (dogs, cats, rats, rabbits, mice, squirrels,
chipmunks, raccoons, opossums, foxes, chickens, humans, etc.). Eggs loosely laid in the hair coat,
drop out most anywhere especially where the host rests, sleeps or nests (rugs, carpets, upholstered
furniture, cat or dog boxes, kennels, sand boxes, etc.). Eggs hatch in two days to two weeks into larvae
found indoors in floor cracks & crevices, along baseboards, under rug edges and in furniture or beds.
Outdoor development occurs in sandy gravel soils (moist sand boxes, dirt crawlspace under the house,
under shrubs, etc.) where the pet may rest or sleep. Sand and gravel are very suitable for larval
development which is the reason fleas are erroneously called "sand fleas."
"Larvae are blind, avoid light, pass through three larval instars and take a week to several months to
develop. Their food consists of digested blood from adult flea feces, dead skin, hair, feathers, and other
organic debris. (Larvae do not suck blood.) Pupa mature to adulthood within a silken cocoon woven by
the larva to which pet hair, carpet fiber, dust, grass cuttings, and other debris adheres. In about five to
fourteen days, adult fleas emerge or may remain resting in the cocoon until the detection of vibration (pet
and people movement), pressure (host animal lying down on them), heat, noise, or carbon dioxide
(meaning a potential blood source is near). Most fleas overwinter in the larval or pupal stage with
survival and growth best during warm, moist winters and spring.
"Adult fleas cannot survive or lay eggs without a blood meal, but may live from two months to one year
without feeding. There is often a desperate need for flea control after a family has returned from a long
vacation. The house has been empty with no cat or dog around for fleas to feed on. When the family and
pets are gone, flea eggs hatch and larvae pupate. The adult fleas fully developed inside the pupal cocoon
remains in a kind of "limbo" for a long time until a blood source is near. The family returning from
vacation is immediately attacked by waiting hungry hordes of fleas. (In just 30 days, 10 female fleas
under ideal conditions can multiply to over a quarter million different life stages.)
"Newly emerged adult fleas live only about one week if a blood meal is not obtained. However,
completely developed adult fleas can live for several months without eating, so long as they do not
emerge from their puparia. Optimum temperatures for the flea's life cycle are 70°F to 85°F and optimum
humidity is 70 percent."-- (Ohio State University Entomology Dept.)
Flea Prevention
Fleas are by nature pests who are capable of spreading germs and causing
discomfort to people and their pets. Some of the problems that
fleas can cause are:
- anemia in young, older or ill pets
- transmission of tapeworms to pets
- transmission of plagues to cats
- rashes to those (people included) who are allergic
Today, there are many methods to rid yourself of these parasites.
In general, keeping a clean home where a pet is present is porbably the
best step in flea prevention. "Washing the pet's bedding and vacuuming
frequently" are good practices in controlling the flea population in your
house. However, it is important to change the vacuum bag and burn the
used bag because a used vacuum bag has the potential to become a flea
incubator (Farley 1996)
There are also numerous lotions and pills that are available through pet
stores and veternarians.
Proban (Cythioate) - is an oral insecticide for dogs which is available
in either liquid or pill form.
Program (lufenuron)- is an oral insect growth inhibitor (IGR) for dogs
available for dogs in pill form. The way it works
is, as your dog takes the treatment, the IGR enters
you dogs blood steam. When a flea takes in
the blood the IGR will be transmitted to the female
flea's eggs disrupting its life cycle.
Program (lufenuron - is the same treatment for cats.
suspension)
Pro-Spot (fenthion)- is a liquid insecticide which is applied to the skin
of a dog in between its shoulder blades. (Farley 1996)