Flea

For other uses, see Flea (disambiguation).

Flea
Scanning electron microscope (SEM) depiction of a flea
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Neoptera
Superorder:	Endopterygota
Order:	Siphonaptera Latreille, 1825
Infraorders
Ceratophyllomorpha Hystrichopsyllomorpha Pulicomorpha Pygiopsyllomorpha
Synonyms
Aphaniptera

Flea is the common name for any of the small wingless insects of the order Siphonaptera (some authorities use the name Aphaniptera because it is older, but names above family rank need not follow the ICZN rules of priority, so most taxonomists use the more familiar name). Fleas are external parasites, living by hematophagy off the blood of mammals and birds. Genetic and morphological evidence indicates that they are descendants of the Scorpionfly family Boreidae, which are also flightless; accordingly it is possible that they will eventually be reclassified as a suborder within the Mecoptera. In the past, however, it was most commonly supposed that fleas had evolved from the flies (Diptera), based on similarities of the larvae. In any case, all these groups seem to represent a clade of closely related insect lineages, for which the names Mecopteroidea and Antliophora have been proposed.

Some well known flea species include:

• Cat flea (Ctenocephalides felis),
• Dog flea (Ctenocephalides canis),
• Human flea (Pulex irritans),
• Northern rat flea (Nosopsyllus fasciatus),
• Oriental rat flea (Xenopsylla cheopis).

Morphology and behavior

Diagram of a Flea

Fleas are small (1/16 to 1/8-inch (1.5 to 3.3 mm) long), agile, usually dark coloured (e.g. the reddish-brown of the cat flea), wingless insects with tube-like mouthparts adapted to feeding on the blood of their hosts. Their bodies are laterally compressed, (i.e., flattened side to side) permitting easy movement through the hairs (or feathers etc.) on the host's body. Their legs are long, the hind pair well adapted for jumping (vertically up to seven inches (18 cm); horizontally thirteen inches (33 cm)) - around 200 times their own body length, making the flea the best jumper out of all animals (in comparison to body size). The flea body is hard, polished, and covered with many hairs and short spines directed backward, allowing the flea a smooth passage through the hairs of its host. Its tough body is able to withstand great pressure, likely an adaptation to survive scratching etc. Even hard squeezing between the fingers is normally insufficient to kill the flea; it may be necessary to crush them between the fingernails or roll them between the fingers.

Hooke's drawing of a flea in Micrographia

Fleas lay tiny white oval shaped eggs. Their larvae are small and pale with bristles covering their worm-like body. They are without eyes, and have mouthparts adapted to chewing. While the adult flea's diet consists solely of blood, their larvae feed on various organic matter including the feces of mature fleas. In the pupae phase the larvae are enclosed in a silken, debris covered cocoon.

Life cycle and habitat

Fleas are holometabolous insects, going through the four life cycle stages of embryo, larva, pupa and imago (adult). The flea life cycle begins when the female lays 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. The eggs take around two days to two weeks to hatch.

Micrograph of a flea larva.

Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, feces and vegetable matter. They are blind and avoid sunlight, keeping to dark places like sand, cracks and crevices, and bedding. Given an adequate supply of food, larvae should pupate within 1-2 weeks. After going through three larval stages they spin a silken cocoon. 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 pupal stages.

Once the flea reaches adulthood its primary goal is to find blood - adult fleas must feed on blood in order to reproduce[1]. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. 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 favourable. Female fleas can lay 500 or more eggs over their life, allowing for phenomenal growth rates.

Evolution and classification

Fleas are apparently related to scorpionflies, winged insects with good eyesight. The flightless snow flea with its rudimentary wings seems to be close to the common ancestor of the 2000 or so currently known varieties of flea, which split off in many directions around 160 million years ago. Their evolution continued to produce adaptations for their specialized parasitic niche, such that they now have no wings and their eyes are covered over. The large number of flea species may be attributed to the wide variety of host species they feed on, which provides so many specific ecological niches to adapt to.

Flea systematics is not entirely fixed. While compared to many other insect groups fleas have been studied and classified fairly thoroughly, details still remain to be learned about the evolutionary relationships among the different flea lineages.

Infraorder Pulicomorpha

• Superfamily Pulicoidea
  • Family Hectopsyllidae – sticktight and chigoe fleas ("chiggers" of Latin America)
  • Family Pulicidae – common fleas
• Superfamily Malacopsylloidea
  • Family Malacopsyllidae
  • Family Rhopalopsyllidae – hosts: marsupials
• Superfamily Vermipsylloidea
  • Family Vermipsyllidae – hosts: carnivores
• Superfamily Coptopsylloidea
  • Family Coptopsyllidae
• Superfamily Ancistropsylloidea
  • Family Ancistropsyllidae

Infraorder Pygiopsyllomorpha

• Superfamily Pygiopsylloidea
  • Family Lycopsyllidae
  • Family Pygiopsyllidae
  • Family Stivaliidae

Infraorder Hystrichopsyllomorpha

• Superfamily Hystrichopsylloidea
  • Family Hystrichopsyllidae – hosts: rats and mice. Includes Ctenopsyllidae, Amphipsyllidae
  • Family Chimaeropsyllidae
• Superfamily Macropsylloidea
  • Family Macropsyllidae
• Superfamily Stephanocircidoidea
  • Family Stephanocircidae - hosts: rodents

Infraorder Ceratophyllomorpha

• Superfamily Ceratophylloidea
  • Family Ceratophyllidae - hosts: rodents and birds. Includes Dolichopsyllidae
  • Family Leptopsyllidae – hosts: mice and rats
  • Family Ischnopsyllidae – hosts: bats
  • Family Xiphiopsyllidae

Relationship with host

Flea bites on the back of a human

Flea bite on the waist of a human with no reaction

Fleas attack a wide variety of warm-blooded vertebrates including dogs, cats, humans, chickens, rabbits, squirrels, rats and mice. 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, however. 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. The bites often appear in clusters or lines, 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. For example, fleas transmitted the bubonic plague between rodents and humans by carrying Yersinia pestis bacteria. Murine typhus (endemic typhus) fever, and in some cases Hymenolepiasis (tapeworm) can also be transmitted by fleas.

Flea treatments

For humans

Flea "dirt" in the fur of a cat is actually excess blood (from host) consumed by the adult flea, passed as feces.

The itching associated with flea bites can be treated with anti-itch creams, usually antihistaminics or hydrocortisone. Calamine lotion has been shown to be ineffective for itching.

Steff2 (talk) 21:28, 9 February 2008 (UTC)Stephanie Kelley===For pets=== The fleas, their larvae, or their eggs can be controlled with insecticides. Lufenuron is a veterinary preparation (Program) that attacks the larval flea's ability to produce chitin but does not kill fleas. Flea medicines need to be used with care as many, especially the acetylcholinesterase inhibitors, also affect mammals. Popular brands of topicals that do not contain cholinesterase inhibitors include Advantage, Advantix, and Frontline and Frontline PLUS.

Even though organophosphate-based insecticides are still sold as flea collars, flea powders and flea shampoos, those are not recommended. Many strains of insects have become resistant against that class of compounds, and they display an unacceptably high level of toxicity against mammals.

There are also commercial and household applications using Cedar oil as a basis for its products that claim to be safe and non-toxic for use in exterminating fleas on pets and in the household which are even said to be able to be used on newborn puppies and kittens for flea control. While this compound is sold through the U.S. by CedarCide Industries which proportedly invented the chemical for the US Army for the control of Sand Fleas and other pests in the Middle East, Cedar oil can be a toxic material when ingested.

Although the company makes claim that their unique formulation prohibits solution migration into the bloodstream and has zero effect on an animals nervous system, or that heavy treatment levels will not create nausea in Cats and Dogs when used for elimination of Flea infestations, that statement is misleading. The use referred to here is strictly EX-ternal, and animals that lick their fur or skin will get the cedar oil into their system which can result in illness, or even death by poisoning which can result in liver failure.

However dangerous Cedar oil products may be to animals, it may be a good product to be used to rid the home & yard of Fleas, Ticks, Bed Bugs, Lice, Mites and other parasites along with Scorpions, Roaches, Ants, Silverfish and even to retard snakes from your property. It is also able to be used for the treatment of all types wood, cloth & leather furniture, bed and mattress, carpets and any other surfaces. However, once again, you just have to be sure that animals cannot lick the surfaces where the product has been used inside the home.

For the home

Combating a flea infestation in the home takes patience as for every flea found on an animal there are many more developing in the home. A spot-on insecticide, such as Advantage, Frontline or Revolution will kill the fleas on the pet and in turn the pet itself will be a roving flea trap and mop up newly hatched fleas. The environment ought to be treated with a fogger or spray insecticide containing an insect growth regulator, such as pyriproxyfen or methoprene to kill eggs and pupae, which are quite resistant against insecticides. Frequent vacuuming is also helpful, but you must immediately dispose of the vacuum bag afterwards. Recent studies have shown that vacuuming may kill fleas almost as effectively as insecticides.

Diatomaceous earth can also be used as an effective home flea treatment in lieu of acetylcholinesterase inhibitory treatments or insecticides which carry with them a risk of poisoning for both humans and animals. Diatomaceous earth absorbs lipids from the cuticle, the waxy outer layer of insects' exoskeletons, causing them to dehydrate and can be purchased at most gardening suppliers or online. It can then be evenly distributed around the house (especially in corners and near furniture) with any type of shaker (salt shaker, spice shaker, etc.) and then vacuumed away after about 7 days. Diatomaceous earth also has the added benefit of killing many other types of insects that might be residing in your house.

Dried pennyroyal has also been recommended as a natural flea control.

Other

File:Flealarcomuseum.jpg

Moche Flea. 200 A.D. Larco Museum Collection Lima, Peru.

The Moche people of ancient Peru worshipped nature. They placed emphasis on animals and even depicted fleas in their art.

See also

• Anti-itch drug

External links

• Template:Dmoz
• Flea Pest Control Information - National Pesticide Information Center
• Advice about fleas from the Berkeley Parents Network
• Links to flea bite pictures (Hardin MD/Univ of Iowa)
• Good Neighbors An essay on the natural history of the flea
• Sand Flea Bite Picture
• Flea As Weapon
• Flea Control Guide
• How to Get Rid of Fleas