Difference between revisions of "Flea" - New World Encyclopedia

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{{Taxobox_begin | color = pink | name = Fleas}}
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{{Taxobox
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{{Taxobox_image | image = [[Image:Scanning_Electron_Micrograph_of_a_Flea.jpg|200px|SEM micrograph of a flea]] | caption = SEM micrograph of a flea}}
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| color = pink
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{{Taxobox_begin_placement | color = pink}}
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| name = Fleas
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{{Taxobox_domain_entry | taxon = [[Eukaryote|Eukaryota]]}}
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| image = Scanning_Electron_Micrograph_of_a_Flea.jpg
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{{Taxobox_regnum_entry | taxon = [[Animal|Animalia]]}}
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| image_width = 200px
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{{Taxobox_subregnum_entry | taxon = [[Metazoa]]}}
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| image_caption = [[Scanning electron microscope|SEM]] of a flea
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{{Taxobox_phylum_entry | taxon = [[Arthropod]]a}}
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| domain = [[Eukaryote|Eukaryota]]
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{{Taxobox_classis_entry | taxon = [[Insect]]a}}
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| regnum = [[Animal]]ia
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{{Taxobox_subclassis_entry | taxon = [[Pterygota]]}}
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| phylum = [[Arthropod]]a
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{{Taxobox_infraclassis_entry | taxon = [[Neoptera]]}}
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| classis = [[Insect]]a
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{{Taxobox_superordo_entry | taxon = [[Endopterygota]]}}
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| subclassis = [[Pterygota]]
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{{Taxobox_ordo_entry | taxon = '''Siphonaptera'''}}
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| infraclassis = [[Neoptera]]
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{{Taxobox_end_placement}}
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| superordo = [[Endopterygota]]
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{{Taxobox_section_subdivision | color = pink | plural_taxon = Families}}
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| ordo = '''Siphonaptera'''
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[[Tungidae]] - Sticktight and [[Chigoe flea]]s (Chiggers) <br>
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| subdivision_ranks = Families
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[[Pulicidae]] - Common fleas<br>
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| subdivision =
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[[Tungidae]]&nbsp;– sticktight and [[chigoe flea]]s&nbsp;(chiggers) <br>
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[[Pulicidae]]&nbsp;– common fleas<br>
 
[[Coptopsyllidae]]<br>
 
[[Coptopsyllidae]]<br>
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[[Vermipsyllidae]] - Carnivore fleas<br>
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[[Vermipsyllidae]]&nbsp;– carnivore fleas<br>
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[[Rhopalopsyllidae]] - Marsupial fleas<br>
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[[Rhopalopsyllidae]]&nbsp;– marsupial fleas<br>
 
[[Hypsophthalmidae]]<br>
 
[[Hypsophthalmidae]]<br>
 
[[Stephanocircidae]]<br>
 
[[Stephanocircidae]]<br>
 
[[Pygiopsyllidae]]<br>
 
[[Pygiopsyllidae]]<br>
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[[Hystrichopsyllidae]] - Rat and mouse fleas<br>
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[[Hystrichopsyllidae]]&nbsp;– rat and mouse fleas<br>
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[[Leptopsyllidae]] - Bird and rabbit fleas<br>
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[[Leptopsyllidae]]&nbsp;– mouse and rat fleas<br>
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[[Ischnopsyllidae]] - Bat fleas<br>
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[[Ischnopsyllidae]]&nbsp;– bat fleas<br>
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[[Ceratophyllidae]]<br>
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[[Ceratophyllidae]]:-fleas mainly associated with rodents
 
[[Amphipsyllidae]]<br>
 
[[Amphipsyllidae]]<br>
 
[[Malacopsyllidae]]<br>
 
[[Malacopsyllidae]]<br>
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[[Dolichopsyllidae]] - Rodent fleas<br>
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[[Dolichopsyllidae]]&nbsp;– rodent fleas<br>
 
[[Ctenopsyllidae]]
 
[[Ctenopsyllidae]]
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{{Taxobox_end}}
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}}
 
'''Flea''' is the [[common name]] for any of the small wingless [[insect]]s of the [[order (biology)|order]] '''Siphonaptera''' (some authorities use the name '''Aphaniptera''' because it is older, but [[circumscriptional name|names above family rank]] do not follow the rules of priority, so most taxonomists use the more familiar name). Fleas are external [[parasite]]s, living by [[hematophagy]] off the [[blood]] of [[mammal]]s and [[bird]]s, and 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 [[fly|flies]] ([[Diptera]]), based on similarities of the larvae.
 
'''Flea''' is the [[common name]] for any of the small wingless [[insect]]s of the [[order (biology)|order]] '''Siphonaptera''' (some authorities use the name '''Aphaniptera''' because it is older, but [[circumscriptional name|names above family rank]] do not follow the rules of priority, so most taxonomists use the more familiar name). Fleas are external [[parasite]]s, living by [[hematophagy]] off the [[blood]] of [[mammal]]s and [[bird]]s, and 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 [[fly|flies]] ([[Diptera]]), based on similarities of the larvae.
  
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''Note'': There is also a genus of [[foraminifera]]n [[Protozoa]] named ''[[Siphonaptera]]''
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''Note'': There is also a genus of [[foraminifera]]n [[Protozoa]] named ''Siphonaptera''
  
 
Some well known flea species include:
 
Some well known flea species include:
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* [[Rat flea|Oriental rat flea]] (''Xenopsylla cheopis'').
 
* [[Rat flea|Oriental rat flea]] (''Xenopsylla cheopis'').
  
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[[Image:Flea_bites.jpg|thumb|left|Flea bites on the back of a human]]
 
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In most cases, fleas are just a nuisance to their hosts, but some people and some animals suffer [[allergic reaction]]s to flea [[saliva]] resulting in [[rash]]es. 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.
 
  
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However, fleas can also act as a [[vector]] for [[disease]].  One possible example of this was the [[bubonic plague]], which may have been transmitted between rodents and humans. Murine typhus (endemic typhus) fever, and in some cases [[tapeworm]]s, ''[[Hymenolepis]]'', can also be transmitted by fleas.
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==Morphology and behavior==
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==Fleas ==
 
 
[[Image:HookeFlea01.jpg|thumb|left|[[Robert Hooke|Hooke's]] drawing of a flea in ''[[Micrographia]]'']]
 
[[Image:HookeFlea01.jpg|thumb|left|[[Robert Hooke|Hooke's]] drawing of a flea in ''[[Micrographia]]'']]
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Fleas pass through a complete life cycle consisting of egg, larva, pupa and adult. 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 its lifetime — usually on the host ([[dog]]s, [[cat]]s, [[rat]]s, [[rabbit]]s, [[mouse|mice]], [[squirrel]]s, [[chipmunk]]s, [[raccoon]]s, [[opossum]]s, [[fox]]es, [[chicken]]s, [[human]]s, etc.). Eggs loosely laid in the hair coat drop out almost anywhere, especially where the host rests, sleeps or nests (rugs, carpets, upholstered furniture, cat or dog boxes, kennels, sand boxes, etc.).  
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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)<ref name=Ohio> [http://ohioline.osu.edu/hyg-fact/2000/2081.html Fleas, HYG-2081-97] William F. Lyon, [[Ohio State University]] entomology page. Accessed 28 December 2006</ref>) - around 200 times their own body length. The flea body is hard, polished, and covered with many hairs and short spines directed backward<ref name=Florida>[http://edis.ifas.ufl.edu/IG087 Fleas] - P.G. Koehler and F. M. Oi. Printed July 1993, revised February 2003. Provided by the [[University of Florida]]</ref>, 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 often insufficient to kill the flea; it may be necessary to crush them between the fingernails.
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Eggs hatch between two days to two weeks into [[larva]]e found indoors in and along floor cracks, crevices, along baseboards, under rug edges and in furniture or beds. Outdoor development occurs in [[sand]]y [[gravel]] [[soil]]s (moist sand boxes, dirt crawlspace under the house, under shrubs, etc.) where the host may rest or sleep. Sand and gravel are very suitable for larval development which is the reason fleas are erroneously called "[[sand flea]]s".
 
  
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[[Image:Fleadirt.jpg|thumb|right|Flea dirt in the fur of a cat]]Larvae are blind, avoid light, pass through three larval [[instar]]s and take a week to several months to develop. Their food consists of digested blood from adult flea [[feces]], dead [[skin]], [[hair]], [[feather]]s, and other organic debris; larvae do not suck blood. [[Pupa]]e 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. "Flea season" is traditionally at the end of summer and in the early fall, but in warmer areas can last year round.
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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.<ref name=BugGuide>[http://bugguide.net/node/view/7040 Order Siphonaptera - Fleas - BugGuide.Net] Accessed 28 December 2006</ref> In the pupae phase the larvae are enclosed in a silken, debris covered cocoon.
  
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Flea [[bite]]s can be treated with [[Calamine lotion]] or 0.5-1% conc. [[hydrocortisone]] cream. [[Lufenuron]] is a veterinary medicine that attacks the larval flea's ability to produce [[chitin]]. See also [[Frontline (medicine)]].
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==Life cycle and habitat==
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Fleas are [[holometabolism|holometabolous]] insects, going through the four [[Biological life cycle|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.<ref name="Florida" /> 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 [[habitat]]s of eggs and developing fleas. The eggs take around two days to two weeks to hatch<ref name="Ohio" />.
  
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==Breaking an infestation==
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[[Image:Flea Larva.jpg|right|thumb|[[Micrograph]] of a flea larva.]]
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[[Image:Flea Larva.jpg|thumb|Flea larva]]
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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 [[silk]]en 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.<ref name="Ohio" /> Fleas are known to [[overwinter]] in the larval or pupal stages.
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Different people have varying sensitivities to the movement of fleas and to their bites.   Some can detect the flea and nab it on the skin; unlucky compatriots only learn of the infestation after a series of rashes erupt the next day.  Some people attract fleas while others never learn about them.
 
  
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<!--- I posted this on the help forum and CnPing here so forgive if it needs fixed a bit user:fabartus 7 April 06 ----->
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Once the flea reaches adulthood its primary goal is to find blood. 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.<ref name="Ohio" /> 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.
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If an animal lives in the home, one should treat it monthly with one of the long duration products as recommended by your [[veterinarian]]. In general, at least in the [[United States]], one should avoid grocery store or pet shop products which are less effective than the prescription strength products from a licensed veterinarian (or the equivalent in [[Commonwealth Nation]]s [[veterinary surgeon]]). These products will keep the fleas off the pets, not off the owners or out of the [[furnishing]]s. More drastic measures are required to protect the owners or unlucky non-pet owner with these ''unwelcome house guests''.
 
  
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To deal with an home infestation one needs to break the [[life cycle]] of the fleas and kill off the breeding age individuals which will otherwise produce a new generation within about 10-18 days, so repeat this technique about every two weeks, ''at least three times''.  
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==Evolution and classification==
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<!--- Source is advice given to many over the years by veterinarian father. user:fabartus --->
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Fleas are apparently related to [[scorpionfly|scorpionflies]]<ref name=Grimaldi>[[David Grimaldi|Grimaldi, D.]] and [[Michael S. Engel|Engel, M.S.]] ([[2005]]). ''Evolution of the Insects''. [[Cambridge University Press]]. ISBN 0-521-82149-5.</ref>, winged insects with good eyesight. The flightless [[snow flea]] with its [[vestigial structure|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.<ref name="Grimaldi" /> 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 niche]]s to adapt to.
  
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=== Area or room treatment ===
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==Relationship with host==
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The goal with this method is to create a vapor cloud of a common inexpensive household pest-control ([[poison]]) above which the breeding population cannot avoid by jumping. This method uses the ubiquitous anti-moth products available at many retail stores, especially [[hardware store]]s (certain) and perhaps grocery stores.
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[[Image:Fleabite.JPG|thumb|left|Flea bites on the back of a human]]
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Fleas attack a wide variety of [[warm-blooded]] [[vertebrate]]s including dogs, humans, chickens, rabbits, squirrels, rats and mice. Fleas are a nuisance to their hosts, causing an [[itch]]ing 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 reaction]]s to flea [[saliva]] resulting in [[rash]]es. 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.
  
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#The best area method would be to place [[moth crystal]]s (flakes) and [[moth ball]]s in the infested areas periodically for several hours at a time; this needs to be done thoroughly, placing moth balls about the floor and on couches, beds, and wherever there are fabrics within a foot or so from the floor. In particular, large area items like couches, and beds need to be individually sprinked across more than 50% of their surface area. Moth flakes are more volatile and would be the better product on these furnishings. Exact placement of the material is not necessary (e.g., some flakes fall into cracks), as the [[vapor]]s spread both outwards and down.
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Besides the problems posed by the creature itself, fleas can also act as a [[vector (biology)|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 [[tapeworm]]s, ''[[Hymenolepis]]'', can also be transmitted by fleas.
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#One should block off the area's (or room's) egress with towels under doors or sheets (bedding or plastic types) taped across the doorways. All ventilation (forced hot air [[furnace]]s and [[air conditioner]]s) should be shut off until after the treatment.
 
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#The area should be vacated by humans and pets and the area allowed to 'soak' for two to three hours.
 
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#Before use, the vacuum cleaner should be cleaned. Then, the vacuum cleaner should be used to vacuum up the flakes or balls and transfer them into a plastic bag or container for reuse for the next treatment in two weeks. Leaving moth balls or flakes under beds in closets, behind dressers, etc. is recommended, as any leftover fleas may be sickened or killed. As the vapors stay low, this should be safe if performed in moderation. Anything that is likely to inhibit the growth of hatchlings will aid the eradication effort.
 
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#This cleaning process should be repeated two to three times, with each cleaning two weeks apart. If the home being treated is in a sub-tropical clime subject to a higher humidity like the American south (say below the [[Mason-Dixon line]]), then the number of treatments should be increased up to five or six times overall. If a flea bite occurs anytime afterwards, the treatment process should be performed again.
 
  
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===Whole home treatment===
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== Flea treatments ==
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For a particularly widespread infestation, one should follow the above strategy with [[insecticide bomb]]s. Chain home stores sell four packs at a cheap price compared to singletons purchased from hardware stores.  The objective is to kill the immature hatchlings before they mature and lay more eggs.  The first downside to this method is that it requires vacating the premises for several hours.  However, the main downside to this method is the need to protect foodstuffs; therefore, the user is strongly urged to read all directions carefully.  This method is generally practiced in commercial restaurants once or twice monthly, so some due caution is warranted, but managable with appropriate safeguards.
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[[Image:Fleadirt.jpg|thumb|right|Flea "dirt" in the fur of a cat, is actually excess blood (from host) consumed by the adult flea, passed as feces.]]
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Flea [[bite]]s can be treated with [[Calamine lotion]] or 0.5-1% conc. [[hydrocortisone]] cream. [[Lufenuron]] is a veterinary medicine that attacks the larval flea's ability to produce [[chitin]]. See also [[Frontline (medicine)]].
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If the home is carpeted throughout, whole home treatment would generally be preferred, as there is no way of knowing where the fleas may be at any moment.  However, if the home contains mostly hard flooring, the using mothflakes/mothballs would be the better method, as problem areas that need to be treated can be specifically targeted, although it is possible that some infested areas could be missed with the targeted method.
 
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With the first method, one can leave the barriers in place for a few weeks if necessary, and naturally, the two methods can be used simultaneously.
 
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===Individual treatment===
 
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Consumption of aged [[garlic]] is purported to be a natural flea repellant, as the fleas do not like the different taste of blood it creates. This consumption based prophylatic treatment may take far longer than conventional methods. Un-aged garlic can cause a toxic fatal reaction in some household pets, so caution should be used in choosing the correct product.
 
  
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Apply [[Frontline (medicine)|Frontline]] or [[lufenuron]] (Program) on pets as directed.
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Flea medicines need to be used with care. [[Phenothrin]] (85.7%) in combination with [[Methoprene]] was a popular topical flea/tick therapy for felines. Phenothrin kills adult fleas and ticks. Methoprene is an insect growth regulator that interrupts the insect's life cycle by killing the eggs. However, the US [[EPA]] has pressured at least one manufacturer of products containing these compounds to voluntarily withdraw some products and include strong cautionary statements on others, warning of adverse feline toxicity.  The Phenothrin was believed to be the cause of the adverse reactions <ref>[http://www.epa.gov/pesticides/factsheets/flea-tick-drops.htm EPA: Pesticides - Hartz Flea and Tick Drops for Cats and Kittens to be Phased Out]</ref>
  
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[[Baking soda]] mixed with equal amount of salt kills fleas. It is rubbed into a pet's fur, pet's bedding, and the carpet. It can kill adult fleas by irritating their chitinous exoskeletons and causing dessication. Wash/rinse pet after treatment to avoid a skin problem. Do not dust the carpet on a rainy day, as the salt will absorb moisture from the air, causing the carpet to become wet. [http://frugalliving.about.com/cs/tips/a/blbakingsoda1.htm]
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A combination of etofenprox (55.0%) and [[pyriproxyfen]] (2.2%) is another formulation used in Sergeant's Gold treatment for cats, and possibly others.
  
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While killing live fleas is a noble proposition, the true threat comes from their scattered eggs that resist even machine washing,  Those with an energy intensive kitchen can freeze their sheets and clothing to guarantee that the adults and the eggs perish.  This has been 100% effective when combined with a cleansing shower.
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Fleas can be controlled in dwellings by application of [[borax]], [[diatomaceous earth]], and other [[insecticides]] to floors, furniture and carpeting.
  
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[[Category:Pest insects]]
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== References ==
 +
<references/>
  
 
== External links ==
 
== External links ==
 +
{{commonscat|Siphonaptera}}
 +
* {{dmoz|Science/Biology/Flora_and_Fauna/Animalia/Arthropoda/Insecta/Fleas/}}
 
* [http://parents.berkeley.edu/advice/health/fleas.html Advice about fleas] from the Berkeley Parents Network
 
* [http://parents.berkeley.edu/advice/health/fleas.html Advice about fleas] from the Berkeley Parents Network
 
* [http://www.lib.uiowa.edu/hardin/md/fleabites.html Links to flea bite pictures (Hardin MD/Univ of Iowa)]
 
* [http://www.lib.uiowa.edu/hardin/md/fleabites.html Links to flea bite pictures (Hardin MD/Univ of Iowa)]
 
* [http://www.primalnature.org/wildlife.html Good Neighbors] An essay on the natural history of the flea
 
* [http://www.primalnature.org/wildlife.html Good Neighbors] An essay on the natural history of the flea
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*[http://ohioline.osu.edu/hyg-fact/2000/2081.html Ohio State University Fact Sheet] Life cycle and control methods for fleas
 
 
*[http://www.petloveshack.com/flea.html Breaking the Flea Cycle]
 
*[http://www.petloveshack.com/flea.html Breaking the Flea Cycle]
 +
*[http://pests.in/fleas.html How to get rid of fleas]
 
*[http://eastvillagepodcasts.com/2006/06/13/my-foot-and-sand-flea-bites/ Sand Flea Bite Picture]
 
*[http://eastvillagepodcasts.com/2006/06/13/my-foot-and-sand-flea-bites/ Sand Flea Bite Picture]
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*[http://www.wood.army.mil/chmdsd/Army_Chemical_Review/pdfs/Jul-Dec%202005/Kirby.pdf Flea As Weapon]
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{{credit|67159531}}
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{{credit|113534721}}
  
  

Revision as of 15:35, 11 March 2007

Fleas
SEM of a flea
SEM of a flea
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Subclass: Pterygota
Infraclass: Neoptera
Superorder: Endopterygota
Order: Siphonaptera
Families

Tungidae – sticktight and chigoe fleas (chiggers)
Pulicidae – common fleas
Coptopsyllidae
Vermipsyllidae – carnivore fleas
Rhopalopsyllidae – marsupial fleas
Hypsophthalmidae
Stephanocircidae
Pygiopsyllidae
Hystrichopsyllidae – rat and mouse fleas
Leptopsyllidae – mouse and rat fleas
Ischnopsyllidae – bat fleas
Ceratophyllidae:-fleas mainly associated with rodents Amphipsyllidae
Malacopsyllidae
Dolichopsyllidae – rodent fleas
Ctenopsyllidae

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 do not follow the 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, and 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.

Note: There is also a genus of foraminiferan Protozoa named Siphonaptera

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

Hooke's drawing of a flea in Micrographia

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)[1]) - around 200 times their own body length. The flea body is hard, polished, and covered with many hairs and short spines directed backward[2], 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 often insufficient to kill the flea; it may be necessary to crush them between the fingernails.

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.[3] 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.[2] 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[1].

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.[1] 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 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.[1] 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[4], 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.[4] 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.

Relationship with host

Flea bites on the back of a human

Fleas attack a wide variety of warm-blooded vertebrates including dogs, 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 tapeworms, Hymenolepis, can also be transmitted by fleas.

Flea treatments

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

Flea bites can be treated with Calamine lotion or 0.5-1% conc. hydrocortisone cream. Lufenuron is a veterinary medicine that attacks the larval flea's ability to produce chitin. See also Frontline (medicine).

Flea medicines need to be used with care. Phenothrin (85.7%) in combination with Methoprene was a popular topical flea/tick therapy for felines. Phenothrin kills adult fleas and ticks. Methoprene is an insect growth regulator that interrupts the insect's life cycle by killing the eggs. However, the US EPA has pressured at least one manufacturer of products containing these compounds to voluntarily withdraw some products and include strong cautionary statements on others, warning of adverse feline toxicity. The Phenothrin was believed to be the cause of the adverse reactions [5]

A combination of etofenprox (55.0%) and pyriproxyfen (2.2%) is another formulation used in Sergeant's Gold treatment for cats, and possibly others.

Fleas can be controlled in dwellings by application of borax, diatomaceous earth, and other insecticides to floors, furniture and carpeting.

References
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  1. ↑ 1.0 1.1 1.2 1.3 Fleas, HYG-2081-97 William F. Lyon, Ohio State University entomology page. Accessed 28 December 2006
  2. ↑ 2.0 2.1 Fleas - P.G. Koehler and F. M. Oi. Printed July 1993, revised February 2003. Provided by the University of Florida
  3. ↑ Order Siphonaptera - Fleas - BugGuide.Net Accessed 28 December 2006
  4. ↑ 4.0 4.1 Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5.
  5. ↑ EPA: Pesticides - Hartz Flea and Tick Drops for Cats and Kittens to be Phased Out

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