The Fleas
By Arnold Sciberras
As if a long day at work isn’t enough. You arrive home and immediately try to relax a bit on the couch. The areas where your socks end on your legs start itching. You quickly realize you are not alone….you are accompanied by a creature this article is dedicated for.
‘Flea’ is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living on the blood of mammals (including humans) and birds. In the past, it was most commonly thought that fleas had evolved from the flies (Diptera), based on similarities of the larvae. Now it is more certain that they are descendants of the Scorpionfly family Boreidae, which are also flightless. There are around 2000 species of fleas known worldwide and the number of local species is yet to be determined.
Fleas are small, agile, usually dark coloured (for example, the reddish-brown cat flea), wingless insects with tube-like mouth-parts adapted to feeding on the blood of their hosts. Their legs are long, the hind pair well adapted for jumping vertically up to 18 cm and horizontally up to 33 cm. This is around 200 times their own body length, making the flea one of the best jumpers of all known animals (in comparison to body size), second only to the froghopper. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothing). The flea body is hard, polished, and covered with many hairs and short spines directed backwards, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by such as mashing and scratching. Even hard squeezing between the fingers is normally insufficient to kill a flea.
Fleas are insects that carry out complete metamorphosis, which consists of four stages: egg, larva, pupa and adult. The flea life cycle begins when the female lays the eggs after feeding. Adult fleas must feed on blood before they can become capable of reproduction. Eggs are laid in batches of up to 20 or so, usually on the host itself, which easily roll onto the ground. As such, areas where the host rests and sleeps become one of the primary habitats of eggs and developing fleas. Fleas lay tiny white oval shaped eggs better viewed through a loupe. The eggs take around two days to two weeks to hatch. They are blind and avoid sunlight, keeping to dark places like sand, cracks and crevices, and bedding. The larva is small, pale, has bristles covering its worm-like body, lacks eyes, and has mouthparts adapted to chewing. The larvae feed on organic matter, especially the feces of mature fleas, but also feed on dead insects and vegetable matter.
Given an adequate supply of food, larvae should pupate and weave a silken cocoon within 1–2 weeks after 3 larval stages. After another week or two, the adult flea is fully developed and ready to emerge from the cocoon. They may however remain resting during this period until they receive a signal that a host is near - vibrations (including sound), heat, and carbon dioxide are all stimuli indicating the probable presence of a host. Fleas are known to overwinter in the larval or pupae stages.
Once the flea reaches adulthood its primary goal is to find blood as it is the only diet for adult fleas. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. As previously mentioned, adult fleas must feed in order to reproduce. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae, and 5 percent adults. Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are favorable. Female fleas can lay 500 or more eggs over their life. Adaptation can be clearly observed in Rabbit Fleas (Spilopsyllus cuniculi) Bergħud tal-Fniek. Adult females of this species can detect the changing levels of cortisol and corticosterone, hormones in the rabbit's blood that indicate she is getting close to giving birth. This triggers sexual maturity in the fleas and they start producing eggs. As soon as the baby rabbits are born, the fleas make their way down to them and once on board they start feeding, mating, and laying eggs. After 12 days, the adult fleas make their way back to the mother. They complete this mini-migration every time she gives birth.
Fleas attack a wide variety of warm-blooded vertebrates including dogs, cats, mice, chickens, rabbits, squirrels, rats, ferrets, and humans. The most common species include Cat Flea (Ctenocephalides felis) Bergħud tal-Qtates. The primary host of this species is the domestic cat, but this is also the primary flea infesting dogs in most of the world. The cat flea can also maintain its life cycle on rabbits, rodents, ruminants and humans can be infested or bitten, but a population of cat fleas cannot be sustained by these aberrant hosts. The Dog Flea (Ctenocephalides canis) Bergħud tal-Klieb, is very similar in habit to the cat flea but it is more commonly found in Europe. On the other hand, the Human Flea (Pulex irritans) Bergħud tal-Bniedem, is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum.
Fleas are a nuisance to their hosts, causing an itching sensation which in turn may result in the host attempting to remove the pest by biting, pecking, scratching, etc the vicinity of the parasite. Fleas are not simply a source of annoyance. Some people and animals suffer allergic reactions to flea saliva resulting in rashes. Flea bites generally result in the formation of a slightly-raised swollen itching spot with a single puncture point at the center (similar to a mosquito sting). The bites often appear in clusters or lines of two bites, and can remain itchy and inflamed for up to several weeks afterwards. Fleas can also lead to hair loss as a result of frequent scratching and biting by the animal, and can cause anemia in extreme cases. Besides the problems posed by the creature itself, fleas can also act as a vector for disease. A very famous example is the Black Death, which killed millions of people in Europe because of a flea species which was common on Black Rats, which acted as a vector for the bacterium Yersinia pestis. Fleas that specialize as parasites on specific mammals may use other mammals as hosts; humans are therefore susceptible to the predation of more than one species of flea.
For more info: http://arnoldsciberras.blogspot.com/ and www.fortpestcontrol.com
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