TECHNIQUE

Use of Light Traps for the Collection of Adult Mosquitoes (Disease Investigation & Control - Treatment and Care)

Summary Information
Type of technique Health & Management / Managing for West Nile Virus Infection / Techniques:
Associated pages
Synonyms and Keywords
  • New Jersey Light Trap
  • CDC Light Trap
  • CDC Miniature Light Trap
Description Light traps are a means of collecting adult mosquitoes by using their attraction to light. They provide an objective measure of mosquito activity.
  • Traps are usually placed in a known mosquito area, in a secure location out of sight of the public.
    • Parks, golf courses or backyards of cooperative persons may be utilised.
  • They are usually suspended at about 6ft (2 metres) above ground level from a post or tree, 30 feet (10 metres) or more from buildings, in open areas near trees and shrubs.
  • The attractiveness of light traps to many mosquitoes may be increased by using them with carbon dioxide (CO2): a small block of dry ice is wrapped tightly in newspaper or placed in a padded shipping envelope placed in a small cold container designed to allow CO2 gas to escape and is suspended a few inches above the light trap.
  • Collected mosquitoes are gathered every morning and placed in a correctly labelled container until the catch can be sorted with identification and counting of the mosquitoes present.
  • Traps should be used on a regular schedule, one to seven nights per week.
  • Traps should be in position and operational from just before dark until just after daylight.

Different light traps are available:

  • The New Jersey light trap is durable and may be switched on and off manually, used with an automatic timer or used with a photo-electric cell to control its operation. It requires a 110-volt power source and is only suitable for use where an appropriate power supply is available. It may be fitted with a killing jar or with a fine mesh collecting bag if live specimens are required.
  • The CDC miniature light trap is designed to be portable. 
    • It weighs 1.75 pounds, is easily disassembled for transport and works off four D cell (1.5 volt) batteries or one six volt motorcycle battery, with either providing sufficient power for a full night of operation. 
    • The catch is collected in a large nylon collecting bag, which may be protected in areas of heavy rain by having a plastic bag placed upside down over it, with the open end of the bag allowing unobstructed air flow through the trap and collecting bag. 
    • Mosquitoes in the trap are held alive until they can be frozen. 
    • The batteries provide power for one night and the motor (widely available from hobby shops) may be expected to work for 15-25 nights before it wears out. (D70)
    • May be combined with CO2 or octanol as an additional attractant.
  • The CDC trap also may be used with CO2 and no light to collect Culex tarsalis mosquitoes.
  • Trap efficiency may be increased by placing the trap near an oviposition site attractive to female Culex spp. mosquitoes.
    • Such placement may increase the chance of trapping females which have had at least one blood meal and are more likely to be infected with virus. (D73)

(D68, D70, D73)

Appropriate Use (?)
  • For the collection of adult, flying mosquitoes which are attracted to light.
  • May be used as part of risk assessment in determining the relative abundance of mosquitoes
  • May be used for monitoring and assessing the effectiveness of control measures, by comparing collections before and after such control measures are applied.
  • To determine infection rates and reproductive age of mosquitoes (requires collection of live mosquitoes).
  • To obtain an estimate of mosquito population size (live or dead mosquitoes may be collected).
  • New Jersey Light Traps set up in permanent locations may be used to document long-term changes in mosquito populations.
Notes
  • The number and species of mosquito collected in a given type of light trap may be affected by trap placement including height and proximity to cover, proximity to breeding sites and other factors.
  • Different trap types may catch different numbers of mosquitoes. For example the CDC miniature light trap catches about half the number of mosquitoes as either a New Jersey or American light trap.
Complications/ Limitations / Risk
  • Only the flying population of mosquitoes are attracted.
  • There is considerable variation in the degree to which different mosquito species are attracted to light traps. Some species of mosquitoes are not attracted to light and may even be repelled by it e.g. Culex quinquefasciatus.
  • The use of light traps may be limited in the presence of other light sources such as roadside lamps, moonlight and "urban glow"; this applies more to the CDC light trap than to the New Jersey light trap.
  • For many species trap catches fluctuate with the phases of the moon, the largest collections being made during the dark phase. 
  • Should not be placed near other lights.
  • Should not be placed in areas subject to strong winds.
  • Should not be placed near industrial plants that emit smoke or fumes.
  • Need to be used in conjunction with other methods of sampling mosquitoes if information is to be gathered.
  • Culex pipiens complex - Northern house mosquitoes are less attracted to CDC miniature light traps than to New Jersey light traps, making these traps less useful for sampling of these mosquitoes. (D73)
  • Catch may vary between nights therefore if catches are used to decide on actions such as use of adulticides, counts from e.g. three consecutive nights, not from one night only, should be used. (D73)
  • Catches using CDC light traps may be relatively variable.
(D68, D70, D73)
Equipment / Chemicals required and Suppliers
  • Light trap of an appropriate design with killing jar or collecting bag.
  • Power source as required for the light trap (mains supply or batteries, depending on the type of trap).
  • Dry ice if a CO2 source is required.
Expertise level / Ease of Use
  • Expertise is required for correct siting of light traps, for identification of mosquitoes caught in traps, for virus isolation/ identification (if required) and for analysis of results.
Cost/ Availability
  • Costs are variable depending on the type and number of traps used.
Legal and Ethical Considerations --
Author Debra Bourne (V.w5)
Referee Suzanne I. Boardman (V.w6); Becki Lawson (V.w26)
References D68, D70, D73

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