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Siphonaptera
FLEAS
Life   Insecta

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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 host’s 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)

Phylogeny
Taxonomic Category Scientific Name Common Name
Phylum Arthropoda Arthropods
Class Insecta Insects
Order Siphonaptera Fleas

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 vertebrates. 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.
  • Pro-Spot (fenthion)- is a liquid insecticide which is applied to the skin of a dog in between its shoulder blades. (Farley 1996)

Links to other sites

References
  • Farley, Dixie. "Fighting Fleas and Ticks" FDA Consumer Magazine July 22, 1996.(No other info available.)
  • Milne, Lorus and Margery. The Audubon Society Field Guide to North American Insects and Spiders" Chanticleer Press 1980, p. 629.
  • Urguhart, F.A. "Introducing the Insect" Frederick Warne and Co. LTD. 1965, p.241-243.

Acknowledgements
Keith Lee, Ecology major, University of Georgia Athens.
Thanks to Sabina Gupta, Denise Lim, and Dr. John Pickering for technical and web support in developing this page.

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Following modified from University of Guelph
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Order - SIPHONAPTERA
(Greek, siphon = tube; pteron = wing)
Common Name: fleas
Distribution: Cosmopolitan

Description
Nothing on earth resembles a flea, so recognition of these compressed little bloodsuckers should be no problem.

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Following modified from Introduction, Zoological Institute, St.Petersburg, Russia
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Introduction  


Zoological Institute
FLEAS HOME PAGE


Flea - habitus 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 host’s fur, unlike free blood-suckers, such as, for example, Diptera or some bugs.


Flea - parts of body Fleas are secondarily wingless insects. Their body is flattened on the sides and is represented by 3 major parts, or tagma: head, thorax, abdomen. Thorax of fleas is provided with three pairs of legs, the hind legs are the longest. The shape of the head, the flat body shape and prehensile claws of legs help it to move easily through host’s wool. Length of jump some flea species attains 32 cm, average body length being from 1 to 5 mm. Colour of flea body may be light yellow, yellowish black, brown black or jet-black.


 

Fleas are widely spread on all continents, Antarctica included. They occur on hosts and in their nests in all types of habitats from the equatorial deserts and tropical rainforests to the northernmost regions of Arctic tundra. In general in Eurasia as in other continents the largest number of species and genera of fleas occur in several regions with temperate subtropical climate and predominance of mountain landscapes. The most numerous flea fauna is known for Eurasia.

Representatives of the order are known as vectors of plague microbes, murine typhus rickettsiae and some jther pathogens. The great practical significance of fleas determines the necessity to study their fauna for the entire world and separate regions and to elaborate of systematics of the order. Epidemiological significance of fleas determined the great interest of specialists from different countries of the world. The world fauna of this relatively small insect order had been mainly studied by the 1970s-1980s. However classification and phylogeny of the order has not been elaborated completely. No extensive reviews on the fauna of the former Soviet Union and the USA have been published yet.

The elaboration of the natural system of the order, however, is complicated because all fleas are highly specialised parasites. Only a few specimens of fossil fleas from Eocene Baltic and Moicen Dominican amber are currently known. In their characteristics they are nearly identical to the recent forms.

Following modified from Biology, Zoological Institute, St.Petersburg, Russia
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Fleas Biology  


Zoological Institute
FLEAS HOME PAGE


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.

Following modified from Morphology, Zoological Institute, St.Petersburg, Russia
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Fleas Morphology  


Zoological Institute
FLEAS HOME PAGE


Recent (after Snograss, 1946) studies of flea morphology were devoted to the anatomy and sensory organs of different imago segments. The head anatomy were studied in a number of species of fleas (Wenk, 1953; Amrine and Lewis, 1978; Wachmann, 1972). Comparative studies have been made of the structure of mouth apparatus (Vashchonok, 1983), antennae (Rothschild, Hinton, 1968; Medvedev, 1982, 1983) and head capsule (Medvedev, 1989a, b). The anatomy Xenopsylla cheopis thorax was studied mostly detail (Lewis, 1961; Rothschild, Schlein, 1975). Comparative studies of thorax were done by Medvedev (1990, 1992a, b).

The genital apparatus (aedeagus and modified abdominal segments) of fleas is described in detail in a number of studies (Peus, 1955; Smit, 1970; Rothschild, Traub, 1971). Gunther (1961) described the genital musculature of fleas. Goncharov (1964) and a number of other workers studied the functions of various genital structures. Others (Traub 1950; Mardon, 1978; Cheetham, 1988) have made a comparative anatomical study of the aedeagus. Scanninig electron microscopy has been used for aedeagus studying (Medvedev, 1984; Cheetham, 1988). This technique and together with light microscope were used in the comparative investigations of the aedeagus of many species of fleas (Medvedev, 1993, 1994).
 

SHORT DESCRIPTIONS OF ADULT TAGMS

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.

Following modified from Distribution, Zoological Institute, St.Petersburg, Russia
   Top | See original

Fleas distribution

Zoological Institute FLEAS HOME PAGE

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, 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.

For more information see the article «The Distribution of Fleas»

Database on zoogeographic disribution of Siphonaptera


Zoogeographical regioning:

Updated: 2017-07-22 12:47:18 gmt
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