The Gravid Trap is a plastic washbasin, filled with a liquid attractant fondly called "Mosquito Soup". The ingredients of "Mosquito Soup" — 114 liters well water, 1/2 kilogram alfalfa hay, 5 grams brewers yeast, 5 grams malted milk powder — are mixed thoroughly and set for 6 days.
The device on top draws air through a collection chamber (this is important — the mosquito is not drawn through the fan, preserving the specimen). Attracted by the stagnant water, a female mosquito attempts to land on the water surface to lay her eggs. She is then drawn into the collection chamber and trapped.
CMMCP deploys these traps throughout our service area to monitor viral activity. They are moved if needed to sample in as many locations as possible. Mosquito collections (called pools) are sent to the Mass. DPH State Lab. Institute in Jamaica Plain. Notification of positive pools of mosquitoes is given to the CMMCP office and local Board of Health by MDPH. The next response will vary, according to MDPH guidelines, CMMCP recommendations and local BOH desires.