Weekly Female Mosquito Trap Counts

The District uses four types of traps: American light traps, mosquito magnet traps, red boxes and gravid traps which we set out in representative sites of all habitats in Sacramento and Yolo counties. The map below displays the general locations of our weekly traps and how many female mosquitoes were collected during the most recent cycle.

All traps are operated year round and the data is analyzed by District staff. Samples are collected weekly from all traps and transported to the District's main laboratory located at the Elk Grove facility.

The District surveillance system is designed to assess mosquitoes in urban and rural locations. Traps are strategically located throughout Sacramento and Yolo Counties.

Mosquito Magnet Trap
This trap was developed by American Biophysics in 1998. This device collects host seeking mosquitoes (adult mosquitoes looking for a blood meal from a preferred host). This trap is powered by liquid propane and is very portable. It emits carbon dioxide, water vapor, and heat that attract female mosquitoes to the trap. Once a host seeking female mosquito locates the trap it approaches the CO2 outlet and hovers. A fan draws the mosquito into a collection net inside the trap. MMTs are located in either urban or suburban sites. In addition to the surveillance traps, five MMTs are strategically located in the District rice culture regions from May until October to determine if ULV criterion is achieved. This unit operates around the clock.

Gravid Trap
This trap was developed by Reiter in 1983 and updated in 1987. This device collects gravid mosquitoes that are seeking a location to lay eggs. A special mixture of ground meals is added to the trap once a week to replenish the trap's attractiveness. When a gravid adult mosquito approaches this trap a fan positioned over the water pulls the mosquito up into a one way collection container. This trap is very attractive to Cx. pipiens, a potential vector of WNV. A photocell operates the trap from dusk to dawn.

American Light Trap
This trap was developed by Mulheren in 1934. This device collects phototactic (mosquitoes attracted to light) species. A 5 watt compact florescent light is used to attract adult mosquitoes to the trap. Once near the trap the mosquitoes are pulled inside by a small fan and down to a collection jar. A photocell operates the trap from dusk to dawn.

Red Boxes
Red boxes were developed to standardize collections spatially. Different researchers have used red boxes of varying dimensions. Largest catches are made in semi permanent walk-in red boxes which measure 4 x 4 x 6 (Meyer 1985). Smaller 1 x 1 x 1 foot boxes typically collect fewer specimens, but are readily portable. The entrance of the walk-in red box should be left open, draped with canvas, or closed with a plywood door. The canvas or plywood door should have a 1 or 2 ft gap at the bottom to allow entry of mosquitoes, while affording some protection from the wind and decreasing the light intensity within the box. The box entrance should not face eastward into the morning sun or into the predominant wind direction.