Nematocera

• Order Diptera

  Species have one single pair of functional membranous wings, the mesothoracic pair. The metathoracic pair is modified to form halteres or balancers
• Metamorphosis of Diptera

  Complete with apodous and often reduced head larva
• Suborders of Diptera

  • Nematocera
  • Brachycera
  • Cyclorrhapha
• Nematocera

  • Slender, with small, spherical heads and long legs
  • Antennae of adults are longer than the head and thorax
  • Have more than 8 antennal segments
  • No arista
  • Larvae have well-developed head and mandibles that bite horizontally
  • Larvae and pupae are aquatic

  
• Nematocera families

  • Culicidae - mosquitoes
  • Ceratopogonidae - biting midges
  • Simuliidae - black flies
  • Psychodidae - sandflies

  
• Family Culicidae (mosquitoes)


  • Globular head with 2 large compound eyes (no ocelli)
  • Long filamentous antennae with sensory organs and Johnston's organ
  • Mouthparts form an elongated proboscis
  • Proboscis consists of a bundle of stylets loosely encased in a labial sheath
  • Fringes of scales along wing veins and on posterior wing margins
  • Long antennae, legs and mouthparts

  
• Important mosquito genera

  • Anopheles
  • Culex
  • Mansonia
  • Aedes

  
• Anautogeny


  Most female mosquitoes require a blood meal for egg development
• Autogeny


  Some mosquitoes can complete the first ovarian cycle without a blood meal
• Female mosquitoes are attracted by the warmth radiating from the skin of their host
• Mosquitoes are active at night and are attracted by light, hiding in dark corners during the day
• Mosquito activity patterns

  • Aedes - active in morning and evening
  • Culex, Mansonia, Anopheles - usually bite during the night

  
• Mosquito life cycle

  1. Eggs laid on water's edge or on water itself

  2. 4 larval stages feed by filtering organic particles

  3. Pupae (tumblers) do not feed and remain at water surface

  4. Adults emerge from pupal case and fly after 24 hours

  
• Fully developed Aedes larvae remain in eggshell until eggs are flooded, can be stored for up to 4.5 years
• Distinguishing characteristics of Anopheline and Culicine mosquitoes

  • Eggs - Anopheline laid singly, boat-shaped with floats. Culicine laid in rafts or singly (Aedes), no floats
  • Larvae - Anopheline no siphon tube, rest parallel to water surface. Culicine well-developed siphon tube, hang head down
  • Pupae - Anopheline breathing trumpet short and broad, Culicine long and narrow
  • Adults - Anopheline rest with abdomen away from surface, Culicine rest with abdomen towards surface

  
• Mosquitoes lay their eggs on water or in dry places that flood seasonally

  
• Mosquito larvae are air breathers and die in an hour if supply is shut off by an oil film
• Mosquito larvae molt 4 times in less than 2 weeks then pupate

  
• Mosquito pupae are elaborate, free swimming organisms with a large cephalothorax

  
• The pupal stage lasts from 2 days to a week, but a few hours suffice for some dry climate species
• The adult mosquito emerges through a hole in the back of the pupal case as it floats on the water surface

  
• After 24 hours, the mosquito's wings have expanded and hardened and it is able to fly

  
• Mosquitoes need permanent water to breed, and rainfall has a marked influence on their numbers

  
• Heavy rain washes away mosquito larvae and decreases their numbers
• Importance of mosquitoes

  • Vectors of Plasmodium protozoa causing malaria
  • Vectors of arboviruses like yellow fever and dengue
  • Vectors of filarial nematodes causing elephantiasis
• Mosquito-borne diseases

  • Malaria (Anopheles)
  • Yellow fever (Aedes)
  • Dengue (Aedes)
  • Filariasis (Culex, Aedes, Mansonia)
• Control measures against mosquitoes

  • Biological control using larvivorous fish
  • Use of larvicidal compounds
  • Removal or reduction of breeding sites
  • Residual spraying with insecticides like DDT, HCH, dieldrin, malathion
• Family Psychodidae (sandflies or owl midges)


  • Small, dull colored, slender, moth-like, hairy flies
  • Antennae long, 16 segments
  • Wings held rooflike over abdomen during rest

  
• Subfamilies of Psychodidae

  • Psychodinae - moth flies, of little importance
  • Phlebotominae - sand flies, of great importance

  
• Phlebotominae (sand flies)

  • Not as hairy as moth flies, hold wings at 60 degrees from body
  • Mouthparts relatively long, of horse fly subtype with cutting mandibles
• Female sand flies feed on plant fluids and blood by telmophagy, while males feed mainly on plant juices
• Sand flies usually feed at night or twilight, are weak flyers and inactive in wind
• Sand flies require darkness, high humidity, organic debris, and a sleeping host to breed
• Sand fly females are chemically attracted to dead plant material and feces for egg laying
• Sand fly larvae feed on animal feces, decaying vegetation, and fungi
• Sand flies are good vectors of disease despite their weakness and fragility
• Family Simuliidae (black flies or buffalo gnats)

  • Small, stout, 1 to 5 mm long flies with a humpbacked appearance
  • Wings broad and iridescent, with strongly developed anterior veins
  • No scales, covered in short golden or silvery hairs
• Female black fly eyes are separated, while male eyes are contiguous
• Sand flies

  Good vectors of disease, which is surprising considering their weakness and fragility
• Stages of life cycle

  • egg
  • larva
  • pupa
  • adult