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Species |
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l.2.1 |
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| l.2.2 | Pyemotes ventricosus |
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l.2.3 |
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l.2.4 |
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l.2.5 |
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l.2.6 |
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l.2.7 |
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l.2.8 |
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l.2.9 |
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l.2.10 |
Cheyletiella yasguri |
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l.2.11 |
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l.2.12 |
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l.2.13 |
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l.2.14 |
the chigger mite or harvest mite
Harvest mites are the larvae of trombiculid mites. They cause skin irritation, often very severe, for a long time. The animals which can act as host are very numerous: rodents, other small mammals, turtles, lizards, snakes and domestic animals, as well as man. In the man the commonest area of attack on the feet is along the line of the top of the shoes.E.(N) autumnalis has been recorded mainly from Westen Europe.
The unengorged larva is 150-300 m m long, with an unsegmented body, a gnathosome and three pairs of legs.
The total life cycle can be up to 1 year but is greatly influenced by environmental temperature, relative humidity and availability of food source. In temperate zones reproductive activity is confined to the spring and summer, whereas in tropical climates eggs are laid all the year round.
The eggs, measuring about 150 m m in diameter, are deposited in clumps of up to 100 in soil. The eggs hatch after some 7-14 days and the larvae which emerge are very active and swarm over the surface of the soil and onto low vegetation such as grass and low-lying leaves. They tend to congregate on the edges of the leaves or tops of pebbles waiting for a passing vertebrate host and are never more than a few centimetres from the ground. The larvae that do not find a host immediately can withstand starvation for up to 30 days. When a host is found the larvae transfer to it at once and seek out an area where the skin is soft, such as the ears, genitalia, axillae, mammae. These larvae feed upon lymph and skin tissue that they have partially digested by their saliva. Around the partially digested tissue the host forms a proteinic tube so that a strawlike feeding tube (stylostome) is formed. Associated with it is a small congestive elevation of the skin surrounded by a wheal. Engorgement takes on average from 1 to 4 days but on some reptiles may require up to 48 days. The engorged larvae generally fall to the ground after feeding, creep into the surface soil and become quiescent before emerge after 7 days as an octopod nymphs, which, after another week or so, become adults. Nymphs and adults live amongst the surface soil feeding on insects, their eggs and general vegetable debris. The adults are predators and live at a depth of about 1-1.8 m approaching the surface in the warm weather but driven deeper by ground frost. The adults have the tendency to oviposit in the same area year after year.
In America three species are important:
Trombicula (Eutrombicula) alfredduggesi (Oudemans) in America
Trombicula (Eutrombicula) splendens (Ewing) in Eastern U.S.A.
Trombicula (Eutrombicula) batatas ( ) from Southern U.S.A. to Brazil
In Australasia are important:
Trombicula (Eutrombicula) wichmani (Oudemans)
Trombicula (Eutrombicula) hirsti ( )
Pyemotid mites are common parasites of many species of Lepidoptera, Coleoptera and Hymenoptera.P. ventricosus has been frequently recorded in cases of human dermatitis in Europe, North Africa, India, Australia and U.S.A.. It is morphologically very close to P. tritici.
The young females attach to the skin of man and cause a papular dermatitis accompanied by many symptoms: pruritus, headache, fever and perspiration. the site of the bite is marked by a vesicle surrounded by a wheal.
P. ventricosus has been the first mite recognized as cause of allergy in 1923.
Ancona G.,1923:
Booth B.H., Jones R.W., 1952:
straw itch mite
Pyemotes tritici is a common parasites of many species of Lepidoptera and Coleoptera in stored products and forest products. It causes severe human dermatitis. P. tritici is often a pest in insect rearing facilities. These mites are able to paralyse insects 150,000 times their size and their venom is effective in a broad range of insects species.
Only the females are parasitic. They inject an extremely potent venom into their insect prey that cause muscle-contraction and paralysis.
Reproduction in P. tritici is by arrhenotokous parthenogenesis, fertilized eggs developing into females and unfertilized eggs into males. Host-seeking females attach and inject a toxin that cause rapid paralysis of the host. Then pierce the host integument with their chelicerae and feed on the hemolymph until they become replete and physogastric. During this feeding phase, development of offspring begins. Development takes place inside the enlarged opisthosomal sac of these now gravid females with eggs proceeding directly to adults. The adults move through a birth canal and out a birth opening. Immediately upon emergence, females are mated and thus almost always disperse as fertilized adults. Such ovoviviparous development is unusual in mites, but provides maximum protection of immatures during the rapid developmental period (as few as 4 days for adult to adult). These unusual features greatly increase survivorship and host-seeking ability.
The sex ratio for this species is about 1-5% male and 95-99% female
The innate capacity for increase of Pyemotes tritici is extremely high ( every female produce as many as 350 offspring) and is likely to exceed that of any known host for which it might be considered as a biological control agent.
Toxins of P. tritici:
- TxP-HMW
proteins from the high mol. wt (ca.250,000) fraction that induced flaccid-muscle paralysis after 4-12 hours in larvae of Galleria mellonella when injected.
- TxP-LMW
proteins from the low mol. wt fraction that induced a rapid, muscle-contracting paralysis in larvae of Galleria mellonella when injected. These proteins are named:- TxP-I , 27,000 daltons and TxP-II (a mixture of two proteins, of 28,000 and 29,000 daltons respectively)
Bruce W.A., Wrensch D.L.,1990:
Bruce W.A., 1984:
Bruce W.A., 1989:
Bruce W.A., 1980:
Bruce W.A., LeCato G.L.,1979:
Cross E.A., Moser J.C.,1975:
Moser J.C.,1975:
Tomalski M.D., Hutchinson K., Todd J., Miller L.K.,1993:
Tomalski M.D., Bruce W.A., Travis J., Blum M., 1988:
The clover mite
B. praetiosa, about 800 µm in lenght, was find on plants, enter home and building. Commonly infesting grasses and low-growing herbaceous plants such as creeping buttercup, vetch and clover. When occasionally parasitize man its effects are annoyance and itching. It is worldwide in distribution.
Morphologically B. praetiosa is characterise by the first pair of legs considerably longer than the remaining ones, and by four deeply-incised lobes each terminating in a fan-shaped seta, on the anterior edge of dorsal side of the propodosoma.
B. praetiosa lays its eggs in the bark of trees, cracks in the window frames or ledges of houses. Here the mite over-winters either as the adult or egg.In spring the larvae emerge and migrate to any suitable vegetation on which they feed. The fully fed larvae return to the house and moult in the protonymphs which once returns to its feeding ground. After two moults, which involve the same in and out migration, there are the adults. The females continue feeding until ready to return to the building to lay their eggs. This movement between the house and the surrounding vegetation is tipical
In the early summer it is often found in large numbers invading houses.
The genus Bryobia include other species:
the fruit tree red spider mite
It feeds on apples, plums and pears.
Kroidl R., Maasch H. J., Wahl R., 1992:
The cosmopolitan C. eruditus is a free-living predator who catch their prey (mainly Astigmata and young stages of storage moths,beetles and psocids) by means of the tibial claws, pierce it with the chelicerae and then suck out its contents. It is often found in granaries, warehouses, barns, leaf litter and topsoil, ham and cheese dust, house dust and mattress dust, birds and mammal nests. It is a very efficient predators in summer. The females (450-600 µm) are normally parthenogenetic and the unfertilized eggs giving rise to females. Males are rarely found. C. eruditus has two kind of male: a little homomorphic male (280 µm) and a large heteromorphic male (400 µm).
The eggs are laid in heaps and guarded by the female. This maternal solicitude stops other predators. Bloody duel are fight frequently.
the rabbit fur mite
Domestic and wild rabbit fur mite has been reported from various parts of the world as occurring also on cats and dogs and as being a facultative parasite of man. These mites are pear-shaped and are equipped with large grasping palps with strong medioventrally directed claws. The chelicerae are slender, needle-like structures designed for piercing. The females are slightly larger than the males and measure between 500 and 600 µm in length and about 325 µm wide. The sense organ on the genu of leg I is of specific diagnostic value being egg-shaped in C. parasitivorax, heartshaped in C. yasguri, and cone-shaped in C. blakei.
People who are attacked by Cheyletiella invariably recover from their pruritus and erythema when separated from their infested pets, or when their pets were treated for their parasites.
Hirst S.,1917:
Pillers A.W.N.,1925:
Humphreys M., 1958:
Smiley R.L.,1970:
Smiley R.L,1965:
This species produces mange in dogs. Cases of human dermatitis have been recorded in Germany and in the Netherlands in persons in contact with infested dogs.
An other Cheyletiella species, C. blakei Smiley,1970, produces mange in cats.
Rack G.,1971:
Bakker E.L.M., Fain A., 1972:
human hair follicles mite
Members of the genus Demodex are probably the most widespread mites, in terms of geographical distribution and variety of hosts. They parasitize practically every species of warm-blooded animal, including man. They cause demodectic mange in dogs, cows, beef cattle, horses,swine, sheep and goats.
These mites are very small, 100-300 µm long, , worm-like, with four pairs of short, stumpty legs located on the anterior half of the body and no visible setae. The idiosoma appears wrinkled and flexible.In the development there are the following stages: egg- larva-protonymph-deutonymph-adults.
Demodex folliculorum occupy the superficial parts of the follicles of simple hairs, above the level of the sebaceous glands in man.
Leydig F. Von, 1859:
Megnin P., 1877:
Hirst S.,1919:
Sosna C.B., Medleau L., 1992:
Desch C., Nutting W.B., 1972:
This species is also parasite of man. It is shorter, 100-200 µm long, than D. folliculorum. It lives in the sebaceous gland and apparently they consume sebaceous gland cells.
Desch C., Nutting W.B., 1972:
Hirst S.,1919:
