Roles of Insects and Mites as Pests and Parasites, Biology tutorial

Parasitic Mites:

The Parasitic mites are found all over and they are serious ecto-parasites of vertebrates and invertebrates. The given list includes the most significant families.

1) Parasitic mites of mammals, birds and humans:

The members of the parasitic mite families listed given are such generally encountered on or in birds, mammals and even humans. 

Family Sarcoptidae (sarcoptic mites): The Sarcoptic mange (Sarcoptidae) mites are very small arachnids which are parasites of mammals and humans causing the mange infection and the mites spend their life in the epidermis of the skin of their host causing different skin disorders.

Family Psoroptidae (psoroptic mites): Psoroptes ovis is the famous sheep mange mite causing the severe damage to fleece and can even reason for deaths.

Family Knemidocoptidae (scaly-leg mite): The species of this family burrow in the non-feathered regions around the beak, eyes, vent and legs of birds (example: canaries, budgies, finches and so on), causing tiny non-itching, wart-like lesions.

Family Myocoptidae (myocoptic mange mite)

Family Atopomelidae (fur mite): It is the presence of even big numbers is generally not injurious however itching and hair loss might take place if the host is in worst condition.

Family Laminosioptidae (fowl cyst, flesh or subcutaneous mites)

Family Pyroglyphidae (house dust mites): The members of this family are the famous house dust mites causing the asthma, rhinitis and allergies in humans because of antigen they produce. They are mostly a problem all along the South African coast line and particularly KwaZulu/Natal where the humidity is much high.

Family Cytoditidae (air sac mites)

Family Analgidae (feather mites)

Family Demodicidae (follicle mites): The members of this family cause symptoms in the mammals characterized through itching, inflammation and other skin disorders. Blepharitis (that is, inflammation of the eyelids) can as well be caused through Demodex mites. Demodex brevis and D. folliculorum live in net harmony in the hair follicles of the humans.

Family Trombiculidae (chiggers): The members of this family are parasitic in the larval phase on vertebrates and can be vectors of diseases such as typhus. The nymphs and adults are the free living predators.

Family Cheyletiellidae (walking dandruff): The symptoms in animals differ from no signs to intense itching, scales on the skin and loss of hair. The lesions are generally on the dorsum of the animal. Symptoms in the humans comprise multiple red, itchy bumps on the arms, trunk and buttocks. As humans are an irregular host for the mite, the symptoms generally go away in around three weeks.

Family Psorergatidae (sheep itch mite): Infested flocks generally exhibit a range of signs. Most of the sheep exhibit no fleece damage at all, or might encompass some tufting of wool all along the flanks. Some sheep (generally 1%) have harshly damaged fleeces. Itch mites mostly influence older sheep and are hardly ever seen in young sheep.

Family Myobiidae (fur mites): The infestations of such mites might generate local and systematic consequences on the host. Local effects differ from no lesion to pruritis and mild scurfiness and in serious cases to ulceration and bacterial pyoderma, fibrosis, hyperkeratosis, chronic inflammation, parakeratosis and acanthosis. Systematic effects comprise reduced life span and body weight.

Family Macronyssidae (fowl or tropical rat mites): This family includes species of economical significance to poultry farmers and they can even be an irritation to humans causing itching or even dermatitis. 

Family Dermanyssidae (red poultry mites): The Dermanyssidae family includes species of economical significance to poultry farmers and they can even be an annoyance to humans causing itching or even dermatitis.

Family Rhinonyssidae (bird lung mites): They generally feed on the hosts and causes pneumonia and harsh inflammation of the respiratory system; the infestations are frequently fatal.

Family Halarachnidae (lung and ear mites of mammals): Reported to nourish on blood, lymph and epithelial cells. Clinical signs are frequently ansent; however coughing and sneezing episodes have been reported; just massive infections are thought to be a direct cause of the death.

2) Parasitic mites of invertebrates:

Family Varroidae: Varroa destructor consists of a serious threat to honey bees worldwide; luckily the South African bees in fact encompass a 'natural' immunity against such mites.

Family Tarsonemidae: The Acarapis woodii lives in the tracheae of bees and can cause their death, though not of economical significance yet in South Africa.

Family Pyemotidae: Pyemotids or 'straw-itch' mites can cause severe problems in insect cultures as they are much small and therefore hard to control. They poison their hosts. In humans they can cause allergies and dermatitis.

Family Trombidiidae: The members of this family are parasitic on arthropods in their larval phase; however nymphs and adults are free living predators.

Insect Pests:

The categorization of an insect as a pest is a subjective one, depend on its potential damage to human principles. Pest insects can damage agricultural crops, consume and/or damage harvested food and cause illness or unproductively in cattle or other agricultural animals, vector human disease.

A few insects are helpful at one phase of life and a pest at the other phase, for illustration most of the lepidopterans might be serious pests as larvae, as they might be pollinators in adulthood. A few insects which are considered pests (specifically in suburbia) are in reality more advantageous than pestiferous: illustration wasps (that is, predate or parasitize numerous pest insects) or bees (that is, the main pollinators of human food supplies).  

Insects considered pests of a few sort take place among all the main living orders by the exception of Ephemeroptera (or mayflies), Plecoptera (or stoneflies), Odonata, Embioptera (or Webspinners), Trichoptera (or Caddisflies), Neuroptera and Mecoptera. On the contrary, of course, necessarily all insect orders primarily have members that are beneficial, in several respects, with the exception of Phthiraptera (lice), Siphonaptera (or fleas) and Strepsiptera, the three orders whose members are entirely parasitic.

Insects are mainly considered as pests for a diversity of reasons comprising:

  • Direct harm by feeding on crop plants in the field or through infesting stored products.
  • Indirect harm through spreading viral diseases of crop plants (particularly by sucking insects like leafhoppers).
  • Spreading disease between humans and livestock.
  • Annoyance to humans.

Illustrations of Insect Pests comprise: The Phylloxera plague, Migratory locust, Colorado potato beetle, Japanese beetle, Boll weevil, Aphids, Cockroach, Western corn rootworm and Mosquitoes.

Parasitic Insects:

Parasitic insects are much significant ecologically, medically and economically. A wide statement of parasitic which comprises mosquitoes and biting flies would make certain 15 percent of the insects parasitic.


Lice have been a portion of human history as parasites devoid of socioeconomic boundaries. Archaeologists have even found traces of the lice on mummies. Such insects are flattened, wingless and have reduced or no eyes. The eggs (or nits) are glued to the hairs or feathers of the host and there are three immature forms from egg to adult. There are no free living phases and they die if separated from the host.  

Bed bugs:

Bugs of the Family Cimicidae are reddish brown in color, dosoventrally flattened bugs which are instead big (up to 8 mm long) without wings. They are nocturnal feeders which run much fast. They usually are most active around dawn whenever they feed on resting hosts. Daytime hiding places comprise mattress seams or crack in walls or furniture. The bites might cause allergic reactions in a few people however usually cause little reaction. Domestic cleanliness and residual insecticides to hiding places is efficient in controlling the bed bugs.

Reduvid Bugs:

Such bugs are vectors for Trypanosoma cruzi. These are big winged bugs which live in cracks and crevices of poorly made homes or in thatched roofs. They are not picky around the source of their blood meal and will nourish on whatever is obtainable in the habitat. Enhancements in the construction processes, the use of metal instead of thatched roofs and residual insecticides are efficient control measures.


Of the some 2,000 flea species, most of them are parasites of mammals. Historically fleas have had a huge impact as transmitters of the bacteria (that is, Yersinia pestis) that cause the plague. Fleas are bilaterally flattened, generally reddish black and wingless. The adults feed by sucking the blood from host. The larvae nourish on debris and flea droppings on the bedding. Fleas are amazing jumpers. For illustration, general fleas can jump a few 33 cm high. The oriental rat flea can jump more than 100 times its body length.


Flies (Order Diptera) show the most medically significant group of insects. They cause directly or indirectly a million human deaths each and every year. A few flies don't kill however contribute to disfiguring, debilitating diseases of numerous types either as vectors of pathogenic organisms or as the parasites.

Black Flies:

Black flies fit in to the family Simuliidae and are found globally where the females nourish on blood and also plant nectar. Black flies are the vectors of Onchocerca volvulus. Mating takes place in flight, larval development takes place in running water and the flies are thus abundant close to rivers and streams. In the US and Canada, S. venustum are renowned to campers and fishermen. Bites might generate little reaction in a few people, however often small red itching wheals build up as a local reaction. At times black fly fever can outcome that is characterized by headache, nausea, fever and swollen limbs.

Sand flies:

Most of the sand flies don't influence humans; however somewhat parasitize reptiles and amphibians. Though, some do nourish on mammals and birds, comprising humans. Females take a blood meal in addition to plant fluids. Males eat just plant juices. Most of them are night time feeders due to the requirement to avoid hot desiccating environments. They are good vectors of disease and contribute in leismaniasis, bartonellosis and a few viral diseases.

Biting midges:

These are much small flies (less than 1 mm) and are generally daytime feeders which are most obnoxious on calm days as winds simply carry them away. Only females nourish on blood. They act as vectors for different protozoal and viral disease of the domestic animals.


A number of 300 species of mosquitoes have been illustrated with at least 150 of these being in N. America. The life-cycle of mosquitoes needs water for the larval and pupa phases. Adult females can live for 4 to 5 months however during the height of the summer season they might just live a couple weeks. Males might live merely for weeks to a month. Species of mosquito transmit western equine encephalitis, St. Louis encephalitis, yellow fever, filarial worms, dengue fever and malaria.

Tsetse flies:

Such flies of the Glossina species are generally found in Africa where they are vectors of sleeping sickness. They are daytime feeders which are visually fascinated to moving objects. Both the sexes feed entirely on blood, comprising that of humans.

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