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Effectiveness of Mosquito Traps

Effectiveness of mosquito traps is limited, and depends on the attractants used

Commercially available traps often incorporate specific olfactory, visual and thermal cues to attract female mosquitoes looking for blood meals. These attractants are usually used in combination, and the effectiveness of mosquito traps are dependent on the effectiveness of the attractants, strategic placement of traps, and regular maintenance of the traps.

Olfactory Cues

Olfactory cue_carbon dioxide

Carbon Dioxide

Mosquitoes can detect increased carbon dioxide concentrations in the air when seeking hosts for blood feeding.
Many commercial mosquito traps are therefore designed to produce plumes of carbon dioxide to mimic human exhalation.
These traps produce carbon dioxide either through the combustion of propane, or by using dry ice and carbon dioxide cylinders, which require regular and proper maintenance.
Some products claim to emit carbon dioxide produced by photo-catalytic reactions, although these claims have not been validated.
All mosquito species are attracted to carbon dioxide-baited traps.

Olfactory cue_lactic acid

Lactic acid

Lactic acid, is a chemical compound commonly found in sweat after exercising or after having a meal that is high in salt or potassium.
Earlier studies have indicated a positive correlation between levels of lactic acid on human skin and attractiveness to anthropophilic (human-seeking) mosquito species such as Aedes aegypti.
Studies have also shown that lactic acid, when combined with other substances such as carbon dioxide and ammonia, could potentially increase the effectiveness of mosquito traps.

Olfactory cue_octenol

Octenol

Octenol is a substance that can be found in perspiration and breath, and is formed when linoleic acid is broken down by the body.
Mosquito antennae are capable of picking up more than 340 chemical odours produced by human skin, including octenol.
Thus, some traps use octenol lures to attract mosquitoes.
Octenol cartridges or strips in the mosquito traps must be replaced regularly to remain effective.

Olfactory cue_pheromone

Pheromone

Anthropophilic mosquitoes have specialised semiochemical receptors on their antennae, which can be used to detect semiochemicals such as pheromones, at close range.
Studies have shown that semiochemicals influence the preference of the oviposition sites of gravid female mosquitoes, which are looking to lay eggs.
When female mosquitoes lay their eggs, they also deposit mosquito pheromones to signal and help other gravid mosquitoes identify safe breeding sites.
Studies have also revealed that gravid females have a preference to lay eggs in water with conspecific larvae (larvae of the same species ).

Visual Cues

Visual cue_ light

Light

Mosquitoes have two light-sensitive simple eyes.
Traps using light as a visual cue are effective for mosquitoes that are active and bite at night, such as Culex and Anopheles species.
Such traps are not effective for capturing Aedes aegypti (the primary vector for Dengue and Zika viruses), which is predominately a daytime biter.

Visual cue_colour

Colour

Diurnally active mosquitoes, such as Aedes species, are believed to have better developed colour sensitivity than nocturnally active mosquitoes such as Culex species.
Studies have shown that Aedes aegypti mosquitoes have spectral sensitivity, ranging from ultraviolet to orange-coloured light. Studies have also demonstrated that orange-lighted targets, such as lamposts, attract host-seeking Aedes albopictus mosquitoes.
Gravid female Aedes aegypti and Aedes albopictus mosquitoes also have a preference for black ovitraps when seeking oviposition sites.

Visual cue_movement

Movement

Mosquitoes have compound eyes made up of hundreds of tiny lenses, designed for spotting movement and distinguishing prey, particularly useful for day-biters like Aedes aegypti, which may rely more on visual cues.
Movement cues, at closer range, are usually effective in combination with olfactory cues, which attract mosquitoes from a longer range. When a mosquito following the olfactory cues comes nearer, it senses the movement of the host and targets it.

Thermal Cues

Thermal cues_temperature and moisture

Temperature and Moisture

Mosquitoes use thermal sensory information to detect body heat and moisture at close range, when seeking a warm-blooded host.
The maxillary palpus located on the mosquito head is believed to be sensitive to heat, helping the mosquito to locate warm-blooded prey and pinpoint capillaries that are closest to the skin and thus easy to reach.
Studies have shown that mosquitoes have a preference for warmer objects at human body temperature, compared to cooler objects at room temperature.