The flea is a blood-sucking insect that is an important vector of disease and can be a serious pest. Fleas are parasites that live on the outside of the host (i.e. they are ectoparasites). As the main agent of the Black Death (bubonic plague) in the Middle Ages, they were an important link in the chain of events that led to the death of a quarter of the population of Europe.
Origin of the species and description
Fleas form a small group of insects that probably evolved from an ancestor of the Mecoptera (scorpions), with which they share certain characteristics. Both groups have a spiny stomach, sex differences in the number of ganglia in the ventral nerve canal, six rectal glands, and a simple type of ovary.
Males have a similar type of spermatozoa, unique to the phylum Arthropoda, in which a movable flagellum or tail, lacking an outer ring of nine tubules, is housed around mitochondria (cell organelles). Fossil fleas found in Australia are said to be 200 million years old. Two other known fossil fleas come from Baltic amber (Oligocene) and are very similar to “modern” fleas.
Since fleas are capable of jumping horizontal or vertical distances up to 200 times their body length and developing an acceleration of 200 gravity, they have been described as insects that fly with their legs. Some species that live in nests high above the ground or in other unusual habitats crawl rather than jump.
Fun fact: Accidental use of flea's unusual power occurs in “flea circuses” , in which they pull miniature carts and perform other feats.
Appearance and Features
Fleas — they are small, wingless insects with a tough cuticle that have many bristles and broad, flattened spines that are often combed. Adult fleas range in size from about 0.1 to 1 cm in length. About 2,000 species and subspecies of fleas are known, but this order is still small compared to many other groups of insects. However, it is widespread among some, such as the rat flea and the mouse flea, which are carried by people around the world.
Anatomically, adult fleas — a fairly homogeneous but distinctive group, with many interesting modifications and few obvious connections to other species. The compressed body allows them to quickly move through the hair or feathers of the host, while the spines or ridges projecting back serve to secure them inside the fur, hair or feathers.
Their mouths are modified for sucking blood and include spiky needles that aid in both the penetration of fleas into the host's skin and the attachment of species that spend long periods attached to the host (such as sticky fleas). As a rule, fleas living on diurnal hosts have well developed eyes, while species parasitizing on underground hosts (for example, moles) or nocturnal animals (for example, bats) have poorly developed eyes or none at all.
Fun fact: The most impressive flea adaptations — highly developed jumping legs. During their evolution, fleas, like most parasitic insects, lost their wings. However, some parts of the flight mechanism have been retained and incorporated into the jump mechanism.
On flying insects, a rubber protein known as resilin forms the hinge by which the wings are attached to the body. Resilin absorbs the compression and tension created during each wing stroke and the stored energy is transferred through a springy recoil effect to help initiate each subsequent stroke.
Fleas, despite their wingless state, retained elasticity on the chest in the place where the paws are attached to the body. When the flea crouches, the elastic pads are compressed and it is maintained in that state by a muscle-controlled gripping mechanism. In the moment before the jump, the hold muscles relax and the energy in the resilin pads is transferred through the legs. This creates a lever effect that pushes each shin and foot to the ground and thereby makes the flea jump.
Where does the flea live?
Native flea species are found in polar, temperate and tropical regions. Fleas, especially Xenopsylla cheopis, are considered the main carriers of murine (endemic) typhus, a rickettsial disease of humans. The source of infection are rats and mice. Fleas are considered important in the maintenance and spread of many locally limited infections in rodents and other mammals, including tularemia and Russian spring-summer encephalitis.
Fleas transmit myxomatosis, a viral disease of rabbits that is deliberately used to control rabbits in areas where they are a serious pest (eg Australia). Fleas are probable carriers of canine filarial worms and serve as an intermediate host for the common tapeworm (Dipylidium caninum) of dogs and cats, and sometimes children. If severely infested, animals can be severely injured or killed by flea bites and, as a result, lose blood. Fleas are susceptible to parasitism from external mites, internal nematode worms, and bacterial, fungal, and protozoan infections.
The female penetrating flea burrows into its host's skin, usually on the legs, and lives in a cyst that forms around it . Severe itching accompanies the development and expansion of the cyst, as the belly of a pregnant flea grows to the size of a pea; secondary infections can be serious complications.
Now you know where fleas are found and how to deal with them. Let's see what they eat.
What does a flea eat?
Fleas feed exclusively on the blood of mammals (including humans), as well as birds. Flea infestation can lead to severe skin inflammation and severe itching. Although many animals acquire partial immunity after persistent or repeated attacks, individuals (especially humans) can sometimes become sensitized after exposure and develop allergies.
Species that attack humans and livestock include:
- the cat flea (Ctenocephalides felis);
- the so-called human flea (Pulex irritans);
- the dog flea (Ctenocephalides canis);
- sticky flea (Echidnophaga gallinacea);
- the penetrating flea (Tunga penetrans);
- the European chicken flea (Ceratophyllus gallinae), which can parasitize poultry;
- the Western chicken flea (Ceratophyllus niger) in the United States.
Some fleas that feed mainly on rodents or birds sometimes attack humans, especially when their normal host is not present. When rats die from bubonic plague, their hungry fleas, themselves infected with plague bacilli and looking for food elsewhere, can transmit the disease to humans, especially in buildings heavily infested with rats.
Oriental rat flea (Xenopsylla cheopis) is the most effective carrier of plague, but other flea species (eg Nosopsyllus flaviatus, Xenopsylla brasiliensis, Pulex allerans) can also transmit the disease to humans. Although there are cases of plague in tropical and some temperate regions, the disease in humans can be controlled with early diagnosis and antibiotics.
Interesting fact: Plague (forest plague) — a widespread disease among hundreds of species of wild rodents throughout the world, which is maintained in these populations by fleas that parasitize these animals. It is known that more than 100 species of fleas can be infected with a plague bacillus, and another 10 species are carriers of the classic type of urban plague.
Character and lifestyle
Some fleas (such as rabbit fleas) are very specific in their choice of host, while other species parasitize a variety of mammals. The cat flea infects not only the domestic cat, but also dogs, foxes, mongooses, opossums, leopards and other mammals, including humans, if its usual hosts are not available.
Related mammals tend to parasitize fleas, which are themselves related. Thus, rabbit peaks (Ochotona) living in the rocky mountains are infested with two peculiar genera of fleas that are also found on peaks in the mountains of Asia, indicating a close phylogenetic relationship between these geographically separated hosts. Bird fleas have relatively recently adapted to their hosts. They share several features, one of the most obvious of which is an increase in the number of ridges on the upper surface of the chest, which serve to secure them inside the feathers.
Interesting fact: Monkeys do not feed on fleas, as well as horses and most ungulates. The most parasitic group of mammals are rodents. Their habit of building nests in burrows encourages the development of flea larvae. Animals without a permanent home tend to tolerate fewer fleas.
Although both flea sexes feed voraciously and repeatedly on blood, they survive for varying periods of time, regardless of the host. For example, a rabbit flea can survive nine months at temperatures near freezing without feeding.
Social Structure and Reproduction
Lifecycle details only available for several types of fleas. They have four life stages — egg, larva, pupa and adult. Pearly white oval eggs are laid on the body, in the nest or in the habitat of the host animal.
The larva is small and legless and feeds on organic debris such as dried feces, dried pieces of skin, dead mites, or dried blood found in the host's nest. Adult fleas quickly pass freshly absorbed blood through their intestines to produce feces to feed their children, which is necessary for the successful metamorphosis of some species of flea larvae.
After three (on rare occasions two) molts, the larva unrolls a silken cocoon that includes debris from the nest and enters the pupal stage. The pupa turns into an adult in a few days or months. Some species may enter a developmental arrested state at the end of the pupal stage and will not become adults until a host appears. Depending on the species or environmental conditions, the time required for the full life cycle of a flea varies from two weeks to several months.
Fun fact: The lifespan of an adult flea ranges from a few weeks ( for example, Echidnophaga gallinacea) up to a year or more (Pulex allerans).
The life cycle of the European rabbit flea (Spilopsyllus cuniculi) and its host are perfectly synchronized. The sexual development of male and female fleas is under the direct control of rabbit sex hormones. Thus, the eggs of a female flea successfully mature only if she feeds on a pregnant rabbit.
When young rabbits are born, both sexes of fleas mature and leave a mother for chicks and a nest where they copulate and lay eggs, thus providing the flea larvae with a suitable habitat for development. If the female rabbit's sex hormones are artificially controlled by the administration of a synthetic progestin (contraceptive), sexual development of the female flea also stops.
Although a similar case among other flea species is not yet known, it has been documented that rat fleas are less fertile when fed on infant mice than their parents, and that the mouse flea (Leptopsylla segnis) is more fertile when reared more on family units. than in individual adult mice. Therefore, it is likely that the influence of host hormones is more widespread than expected.
Natural enemies of fleas
The enemies of fleas are people who are trying in every way to get rid of them. When dealing with fleas, it is best to treat both the host's nest or bedding area, which is a breeding ground for fleas, and the infested host, as the larval and pupal stages usually develop away from the host's body.
For infected animals, a commercial dust, spray or aerosol containing an insecticide or growth regulator is used. However, in some regions, fleas have become resistant to some insecticides and new materials are required. To control larvae and adult fleas away from the host, insecticides or growth regulators can be applied to pens and shelters of affected animals. Repellents can be effective in preventing flea attacks.
The flea life cycle is interrupted when the temperature drops below 21 degrees Celsius or there is an excessive drop in humidity. Thus, thoroughly cold washing bedding or leaving items outside during frost can help control a potential flea infestation while other measures are in place.
Preventive measures can help avoid rashes and irritation for pets. It is easier to prevent fleas than to get rid of an infestation. It can take up to 6 months to completely remove fleas, as different stages of the flea life cycle can persist in different hidden areas of the home and pets, avoiding vacuum or other physical and chemical measures to kill them.
Population and species status
Although the taxonomic division of flea groups is based on a combination of superficially trivial morphological characteristics, they reflect fundamental differences between groups. At the familial or ancestral level, the classification is based mainly on the shape of the head and thorax, arrangement of combs, modifications of the male copulatory organ and female reproductive organs, general chaetotaxy (arrangement of bristles), and other characteristics.
The flea population today can be divided into several superfamilies, the exact number depending on the classification system used. The overall system recognizes 10 superfamilies, including Pulicoidea, Malacopsylloidea, Ceratophylloidea, Coptopsylloidea, Ancistropsylloidea, Pygiopsylloidea, Macropsylloidea, Stephanocircidoidea, Vermipsylloidea, and Hystrichopsylloidea.
Other systems may recognize five or eight superfamilies. The main system describes the five original superfamilies of an early classification proposed in 1982 by Francis Gerard Albert Maria Smith. Later, other experts built on this system, introducing new groups or combining existing groups based on similarities or differences in the structures of the abdomen, head, and chest.
This system looks like this:
- superfamily Pulicoidea. Includes cat and dog fleas, oriental rat fleas, sticky fleas and human fleas, penetrating, bird and rabbit fleas. Includes the family Pulicidae, with the genera Pulex, Xenopsylla, Tunga and others;
- superfamily Malacopsylloidea. All fleas in this superfamily are found on rodents. Includes 2 families, Malacopsyllidae and Rhopalopsyllidae;
- superfamily Ceratophylloidea. Fleas in this superfamily are found on rodents and bats. All fleas that do not have the character combinations listed in the other 3 superfamilies belong to the Ceratophylloidea, which includes 12 families;
- the superfamily Vermipsylloidea. These are carnivorous fleas. The superfamily contains one family, Vermipsyllidae;
- the superfamily Hystrichopsylloidea. These are basically rodent fleas. They are very common throughout the world. Includes two families, Hystrichopyllidae and Ctenophthalmidae.
The flea is one of the most common parasites of cats, dogs and other furry pets. In particular, it is believed that every cat and dog will suffer from a flea infestation at some point in their lives. Not only are fleas uncomfortable, they can also be very irritating to your pet and make them very unhappy. Therefore, there is an active fight against fleas.