Mosquitoes in Oklahoma

1
Mosquitoes in Oklahoma

• Dr. Russell Wright, Prof. Emeritus

2
General Biology of Mosquitoes

• Insects that belong to Order DIPTERA which
  includes all the flies.
• Have four life stages
• Egg -- laid on surface or edge of water.
• Larvae -- live only in water.
• Pupae -- live only in water.
• Adults

3
Eggs

• Laid on singly on surface or edge of water.
• Some species lay eggs in rafts on surface of
  water.
• Some sp. hatch 24-36 hrs.
• Some hatch after one, two or three years.
• Over wintering stage for some species

4
Larvae

• Four stages 1st, 2nd, 3rd, 4th instars.
• Called wrigglers, very active, come to surface
  for air.
• Total length 6-12 days. Some species even weeks.

5
Pupae

• Stage that changes from larvae to adult.
• Called tumblers very active, come to surface
  for air.
• Stage lasts from 3-6 days.

6
Adult (Male)

• Emerges first
• Feeds on nectar sources for energy.
• Mates within 3 to 7 days and dies

7
Adult (Females)

• Emerges and feeds on nectar.
• Mates, usually only once.
• Searches for blood meal.
• Needs blood meal to develop eggs.
• 1-5 blood meals over life of 7 to 28 days.

8
Mosquito Life Cycle
9
Mosquito Species Present in Oklahoma

• Approximately 60 known species in Oklahoma. Over
  230 species in U.S.
• Usually only 6-8 species will be a nuisance pest
  in any given area.

10
Genus and species

• Every species is more different from each other
  genetically than you and I are from any other
  human on earth.
• So I will need to use at least Genus names,
  sometimes species as I refer to biology.
• Think of these names as the folks you know as
  Jane, Linda, Ann , Tom. Dick, Harry etc.
• However if you think of any of your friends by
  these names, dont tell them I told you to do so.

11
Classification Based on Larval Habitat

• Flood Water Mosquitoes
• Permanent Water Mosquitoes
• Permanent Pool Group
• Transient Water Group
• Container Mosquitoes

12
Larval Habitat

• Important to know which mosquitoes cause problems
  and when.
• Identify larval habitats based on adults present.
• Most effective to find and map larval habitats
  and eliminate or treat in this stage.

13
Flood Water Mosquitoes

• Mosquitoes in Genera Aedes, Ochlerotatus, and
  Psorophora
• Some species from these three genera are the most
  important pest species.
• Bite humans, livestock, pets. And can have very
  large populations in spring and early summer.
• Do not believe that most vector WNV

14
Flood Water Mosquitoes (cont.)

• Eggs are laid on the soil surface at the edge of
  standing pools of water that are left from heavy
  rains or floods.
• Often woodland pools roadside ditches or low
  areas along creeks rivers that collect flood
  water.
• Eggs hatch when flooded by run off from heavy
  rains or flood water.

15
Flood Water Mosquitoes (cont.)

• Eggs are over wintering stage. In most cases must
  spend winter in egg case, called diapause stage.
• Can survive in egg stage for several years until
  flooded.
• However, can have different hatches within
  several days if increased water levels hatch new
  eggs.

16
Flood Water Mosquitoes (cont.)

• Adult populations peak in late April, May, and
  June, some species hatch with late summer fall
  rains .
• Adults die quickly during hot weather.
• Any flooded pools usually dry up too fast to
  support larvae in hot weather.
• Females most active around sunset or in shady
  areas when disturbed.

17
Floodwater Pool Aedes vexans
18
Floodwater Pool Aedes vexans
19
Permanent Water MosquitoesPermanent Pool Group

• Genera Anopheles, Coquillettida, Mansonia some
  Culex sp.
• Found in quiet bodies of freshwater with
  sunlight, much surface vegetation and very
  little wave action.
• Shallow edges of ponds, some lakes backwaters of
  rivers even slow moving streams.
• Never in main lake or pond areas with much wave
  action.

20
Permanent Pool Group (cont.)

• Anopheles lay eggs singly on surface of water,
  each egg with a float.
• Eggs hatch in 24-36 hrs. Many generations a year
  tend to peak mid late summer
• Adults over winter triggered by photoperiod.
• Deep south perhaps cycle can go all year, slower
  in winter.

21
Permanent Pool Group (cont.)

• Genera Coquillettidia and Mansonia
• Mansonia mosquitoes lay eggs in groups attached
  to plant stems underwater Coquillettidia in
  rafts on water surface.
• Larvae insert breathing siphon into plant and
  takes oxygen directly from plant tissues.
  Cattail marshes and similar type water.
• Appear to have one prolonged generation per year
  and at least in south over winter in larval
  stage.
• Not much of a nuisance pest.

22
Permanent Water MosquitoesTransient Water Group

• Genera Culex and Culiseta
• Canals, long standing ground pools or roadside
  ditches, catch basins, storm sewers , clogged
  sewers long standing irrigation pools, water
  often becomes very foul polluted for some species
  others need fairly clean water.
• These mosquitoes lay eggs in rafts on the surface
  of the water.
• Eggs hatch within 24-36 hours.

23
Transient Water Group (cont.)

• These mosquitoes normally over winter in the
  adult stage.
• Adults emerging in late summer or fall do not
  search for a blood meal, but mate and female
  searches for sheltered areas to spend winter.
• Caves, burrows, sewers, basements etc.
• Populations low in spring peak in mid to late
  summer. Vary some with species.

24
Culex spp. Laying Eggs
25
Transient Water Group (cont.)

• Populations of these mosquitoes low in spring.
• Takes awhile to build large populations.
• Peak abundance July-October.
• Many species prefer birds as hosts.
• Are often best vectors of viruses.
• Bite more readily at night.

26
Transient Water Mosquito Habitat
27
Container Mosquitoes

• Certain species in 5-6 Genera
• In nature larvae live in tree holes, rock pools
  even leaf axils.
• Many species now associated with man made
  containers or materials that hold water.
• Tires, cans, buckets , birdbaths, gutters, pet
  water dishes, plant container bottoms that catch
  water, even cans, paper cups etc.

28
Typical Container Mosquito Habitat
29
Asian Tiger Mosquito

• Aedes albopictus
• Larvae in containers of any size.

30
Aedes albopictus Eggs in Container

• Efficient container breeder utilizing available
  sources.
• Eggs laid on surface of water, on sides of
  container, and on stick.
• Immediate egg hatch of some eggs, delayed hatch
  for others.

31
Asian Tiger Mosquito

• First found in OK 1990-91, Tulsa, SE Counties.
• By 2000 was found in all counties we surveyed.
• Most important pest in most areas.
• Bites in mid to late afternoon.
• Abundant from mid June through Sept.

32
Distribution of Asian Tiger Mosquito in Oklahoma
33
Mosquito Species of Greatest Concern

• Belong to Genus Culex
• Include C. pipiens/quinquefasciatus, southern
  house mosquito most likely vector
• C. restuans, C. salinarius, C. tarsalis.
• Note all are permanent water mosquitoes,
  populations peak in summer through fall at same
  time virus activity peaks
• All prefer to feed on birds.

34
Possible WNV Vector Speciesin Oklahoma

• Bridge vectors to humans horses.
• Culex tarsalis Cx. salinarius Permanent
  transient water but not very stagnant
• Aedes vexans floodwater spring through mid
  summer
• Aedes albopictus
• Ochlerotatus triseriatus. Oc. hendersoni
• Container or tree hole species

35
Surveillance

• Knowledge of the mosquito species in a given area
  and relative abundance is necessary in planning
  control measures.
• Some species do not vector WNV, control not as
  important.
• Accurate records must be kept of surveillance
  locations.
• Species I.D. is essential.

36
Larviciding

• Controlling mosquito larvae most effective
  control measure because life stage is confined to
  aquatic habitat.
• Water management by drainage or source reduction.
• Larvicides can be used if drainage not available
  or adequate.
• Not as practical in Oklahoma until we have
  identified larval sites.