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For educational purposes:--

Information on the basics of Entomology


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Entomology:  SIPHONAPTERA 1

Kingdom:  Animalia, Phylum: Arthropoda

Subphylum: Hexapoda: Class: Insecta: Order: Siphonaptera



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Order:  Siphonaptera

           (14 Families)

  General Summary

  Detailed Habits & Morphology

  Diseases Transmitted

  Sample Examinations

  References      Citations


General Summary of Siphonaptera


          Siphonaptera (or Suctoria) are wingless insects that are ectoparasitic on warm-blooded animals.  They are compressed laterally with short antennae positioned in grooves.  They have piercing and sucking mouthparts, maxillary and labial palps are present, coxae are large and the tarsus has five joints.  Metamorphosis is holometabolous.  The larvae are legless and the exarate pupae are enclosed in a cocoon.

These are especially adapted to an ectoparasitic existence by their laterally compressed bodies, prominent tarsal claws, and well-developed legs adapted for running between the host's hairs, and for jumping, and by their mouthparts. They show only a slight relationship to one other order, the Diptera, by certain aspects of their metamorphosis and somewhat by their mouthparts.

          The mouthparts are made up of a pair of long serrated mandibles, a pair of short triangular maxillae with palps, and a reduced labium with palps. There is a short hypopharynx and a larger labrum-epipharynx similar to that of the Diptera. The labial palps, held together, serve to support the other parts, a function which is performed by the labium in the Diptera. In piercing the host, the mandibles are most important and blood is drawn up a channel formed by the two mandibles and the labrum-epipharynx (Borradaile & Potts, 1958).


          The thoracic segments are free and wings are absent. Although the eggs are laid on the host they soon fall off and are afterwards found in little-disturbed parts of the host's habitat.  Therefore, in houses they reside in dusty carpets and unswept corners of rooms.  In a few days the larvae hatch and feed on organic debris.  The legless and eyeless larvae possess a well-developed head and a 13-segmented body.  At the end of the third larval instar a cocoon is spun and the flea changes into an exarate pupa from which the adult emerges.  The whole life cycle takes about a month in the case of Pulex irritans..


          Pulex irritans is the common flea of European houses, but by far the most important economically is the oriental rat flea, Xenopsylla cheopis, which transmits Bacillus pestis, the bacillus of plague, from the rat to humans.  This bacillus lives in the gut of the flea and the faeces deposited on the skin of the host are rubbed into the wound by the scratching which follows the irritation from the bite. Ceratophyllus fasciatus, the European rat flea, also transmits the plague organism as can also Pulex irritans, but since the latter does not live successfully on rats, it is a less dangerous vector (Borradaile & Potts, 1958).


Detailed Habits & Morphology


          All members of the Siphonaptera feed exclusively on warm-blooded animals.  Their mouthparts lack mandibles and a siphon is formed of structures of the labrum, labium and maxillae.  The labium is an elongated  and fleshy covering mechanism.  The maxillae are interlocking and a maxillary sheath is present but not obvious.  A labrum is also present.



          Fleas are apterous but their extinct ancestors are  known to have possessed wings, which was deduced from pleural plates on the thorax.  Hair-like structures called geocomb and corolla comb, are present on the head.  The antennae have three segments and lie in a groove on the head (see ent159).





          The larvae are eruciform with a distinct head capsule.  They do not possess legs but leg-like setae instead.  Larvae are not parasitic.  There is an exarate pupa formed in a cocoon (see ent160).



          There are over 1,100 species identified in the order.  Their general pest status of humans and domestic animals and their ability to vector diseases makes them of great economic importance.


          Role as Parasites. --  Fleas are well adapted to the parasitic habit by being laterally compressed.  They also have a very hard exoskeleton, their legs are developed for leaping and the hairs on their body are directed backward.




Diseases Transmitted by Siphonaptera


          Bubonic Plague. -- The vector of Pasteurilla pestis is the rat flea.  This bacillus wiped out one quarter of the population of London, England.  The fleas search out other hosts as soon as the rat dies.  Transfer is accomplished by (1) defecation on the body and the inoculum is scratched into the wounds, and (2) the flea cannot digest the bacillus, so it regurgitates into the wound made by its mouthparts.


          Sylvanic Plague. -- The vectors are fleas that live on rodent hosts.  This is actually mild type of bubonic plague, which is found in Western North America.  However, humans may also die from infection.


          Chigger Infection. -- The fertilized female flea burrows under the skin and becomes enormously distended.  A serious tropical form is known as Tunga penetrans.


          Also View "Medical Importance".




Details of Insect Taxonomic Groups


          Examples of beneficial species occur in almost every insect order, and considerable information on morphology and habits has been assembled.  Therefore, the principal groups of insect parasitoids and predators provide details that refer to the entire class Insecta.  These details are available at <taxnames.htm>.





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