Mosquitoes

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Mosquitoes
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• More than 3000 species of mosquitoes have been
  described on a world-wide basis. Scientists group
  species by genus on the basis of the physical
  characteristics they share. The 3000 mosquito
  species found in the world are divided among 28
  different genera. The genus Aedes contains some
  of the worst pests. Many members of the genus
  Anopheles have the ability to transmit human
  malaria.

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• There are three genera of medical importance
• Culex
• Aedes
• Anopheles

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Morphology

• 1.      Body small, fragile, 3-6mm long
• 2.      Distinguishing of sexes
• 1)      Antenna plumose in male, pilose
• in female
• 2)      Palp
• 3)      External genitalia
• 3. Mouthparts, piercing and sucking type.
  Proboscis and 6 needles.

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Egg

• Elongate elipsoid, about ½ mm.
• Anopheles egg, The eggs have distinct lateral
  floats.

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• Anopheles sp egg with tuberculated surface and a
  distinct float in the center.
• Anopheles eggs, with a larva emerging. The eggs
  have distinct lateral floats which easily
  differentiates them from culicine eggs.

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Aedes Egg

• Laid singly in or near water.

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Larva (wigglers)

• A newly emerged anopheles (1st instar larva).

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Pupa

• Like a , divided into cephalothorax and
  abdomen. It moves actively but takes no more food.

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Morphological difference of three genera
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Anopheles
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Culex
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Aedes
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Life Cycle of a Mosquito

• Mosquitoes of different species lay their eggs
  in a variety of water sources that range from
  small containers to vast expanses of marshland.
  The larval stage is always aquatic and shuttles
  from the subsurface where it filter feeds on
  micro-organisms to the surface to obtain oxygen
  through a snorkel-like breathing apparatus. The
  pupal stage does not feed but unlike most Insect
  pupae is extremely active. The adult emerges from
  the pupal case using air pressure and assume a
  terrestrial existence.

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Holometabola

• Egg 1-4 days-gt larva (4 stages)
• 7 days -gt pupa 2-3 days ? adult.
• 10-14 days total.

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Habit or Bionomics
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Habit or Bionomics

• Eggs
• Larvae (wigglers or wrigglers)
• Pupae
• Adults

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Larval Habitats of Mosquitoes

• Mosquito larvae can be found in numerous
  habitats. Each habitat produces specific mosquito
  species. Habitats can be generally grouped into
  four types Running Water, Transient Water,
  Permanent Water, or Container.

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Transient Water

• Transient water sources, such as flooded
  areas, snowpools, and ditches are used as
  breeding grounds for mosquito species whose eggs
  can withstand desiccation, such as Aedes.

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Permanent water

• These waters (also known as Semi-permanent)
  are present for extended periods of time and
  support characteristic aquatic vegetation.
  Cattail, rushes and sedges are typical freshwater
  swamp vegetation. Genera associated with
  permanent water are Anopheles, Culex, and so on.

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Containers

• Container water habitat can be found in
  both natural settings, such as water held by
  plants (bromeliads) to artificial settings, such
  as water found in tires. The habitat of
  containers are based on the containers
  themselves. Treehole sites generally have
  tannin-enriched water which is characteristically
  clear, with rotting wood at the bottom. Many
  treehole species now also use artificial sites,
  such as tires since they provide insulation
  against the weather and are more numerous.
  Artificial containers are a convenient mode of
  transporting a species of mosquito outside of
  it's natural range.

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Adult

• 1.     Breeding places
• 2. Hiding and resting places
• dark, poorly ventilated and humid places.

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• 3.      Feeding
• Mosquitoes belong to a group of insects that
  requires blood to develop fertile eggs. Males do
  not lay eggs, thus, male mosquitoes do not bite.
  The females are the egg producers and "host-seek"
  for a blood meal. Female mosquitoes lay multiple
  batches of eggs and require a blood meal for
  every batch they lay.

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• Few people realize that mosquitoes rely on sugar
  as their main source of energy. Both male and
  female mosquitoes feed on plant nectar, fruit
  juices and liquids that ooze from plants. The
  sugar is burned as fuel for flight and is
  replenished on a daily basis. Blood is reserved
  for egg production and is imbibed less
  frequently.

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3.      Feeding

• Finding host
• By sight (movement)
• Detecting infrared radiation
• Chemical signals CO2, lactic acid, etc.

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• Why are some people more attractive to mosquitoes
  than others?
• Scientists are still investigating the
  complexities involved with mosquito host
  acceptance and rejection. Some people are highly
  attractive to mosquitoes and others are rarely
  bothered. Mosquitoes have specific requirements
  to satisfy and process many different factors
  before they feed. Many of the mosquito's
  physiological demands are poorly understood and
  many of the processes they use to evaluate
  potential blood meal hosts remain a mystery.
  Female mosquitoes use the CO2 we exhale as their
  primary cue to our location.

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• A host seeking mosquito is guided to our skin by
  following the slip stream of CO2 that exudes from
  our breath. Once they have landed, they rely on a
  number of short range attractants to determine if
  we are an acceptable blood meal host. Folic acid
  is one chemical that appears to be particularly
  important. Fragrances from hair sprays, perfumes,
  deodorants and soap can cover these chemical
  cues. They can also function to either enhance or
  repel the host seeking drive.

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• Dark colors capture heat and make most people
  more attractive to mosquitoes. Light colors
  refract heat and are generally less attractive.
  Detergents, fabric softeners, perfumes and body
  odor can counteract the effects of color. In most
  cases, only the mosquito knows why one person is
  more attractive than another.

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• 4.        Seasonal Distribution
• Above 10o C, mosquitoes will move from
  their hiding places and become active. In
  Shandong they are prevalent from May to October.

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• 5. Hibernation
• Mosquitoes, like all insects, are cold
  blooded creatures. As a result, they are
  incapable of regulating body heat and their
  temperature is essentially the same as their
  surroundings. In tropical areas, mosquitoes are
  active year round. In temperate climates, adult
  mosquitoes become inactive with the onset of cool
  weather and enter hibernation to live through the
  winter. Some kinds of mosquitoes have winter
  hardy eggs and hibernate as embryos in eggs laid
  by the last generation of females in late summer.
  The eggs are usually submerged under ice and
  hatch in spring when water temperatures rise.

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• Other kinds of mosquitoes overwinter as adult
  females that mate in the fall, enter hibernation
  in animal burrows, hollow logs or basements and
  pass the winter in a state of torpor. In spring,
  the females emerge from hibernation, blood feed
  and lay the eggs that produce the next generation
  of adults. A limited number of mosquitoes
  overwinter in the larval stage, often buried in
  the mud of freshwater swamps. When temperatures
  rise in spring, these mosquitoes begin feeding,
  complete their immature growth and eventually
  emerge as adults to continue their kind.

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• 6.      Life span Males, 1-3 weeks. Females,
  much longer. Hibernating females may live as long
  as 5 months or more.
• 7.      Range of flight 500 meters long and 300
  meters high.

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Mosquitoes and diseases

• 1.      Annoyance pest A mosquito bite may
  induce local dermatitis or even systematic
  reaction in sensitive persons.

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• Child with hypersensitivity to mosquito bites.
  Mosquito bites can produce a severe allergic
  reaction. In this case the child displayed both
  the immediate and the delayed type reactions. The
  scars on the forearms are due to necrotic changes
  which occurred during the delayed type reaction.

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• 2.      Parasitic diseases Malaria and
  filariasis.
• 3.  Virus diseases Japanese encephalitis B,
  mainly by Aedes and Culex tritaeniorrhyncus.
  Dengue fever and yellow fever.
• 4.   Mechanical transmitter Some mosquitoes may
  carry fly eggs to humans, inducing myiasis.

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• Can mosquitoes transmit AIDS?

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Control

• 1. Individual protection by site selection for
  homes, nets or screens, chemical repellents, etc.
• 2.   Elimination of breeding places.
• 3.   Insecticides.
• 4.  Biological Genetic control and protection of
  mosquitoesnatural enemies (bat, dragon fly,
  swallow, Gambusia fish, etc.)