Mosquito News V o l u m e 1 , i s s u e 2 A u g u s t 2 0 0 9 S p e c i a l p o i n t s o f i n t e r e s t : Mosquito Myths Debunked There are many stories circulating about what will control mosquitoes. Most of them are myths. Bats, Purple Martins & Mosquitoes The bat myth started with a study that counted the number of mosquitoes eaten by bats in a closed room with only mosquitoes present. The bats ate about 10 per minute, which was extrapolated out to 600 per hour. While bats will feed on many different insects, they do not seem to prefer mosquitoes and will often go after larger prey such as beetles or moths. Other studies analyzing stomach contents of bats show that less than one percent of their diet is mosquitoes. Purple martins eat a large variety of flying insects but are not overly fond of mosquitoes. A seven-year study conducted by the Purple Martin Conservation Association did not find a single sample (out of 500) containing any mosquitoes. Purple martins actively feed during the day and most mosquitoes are active at dusk or after dark. Even though Asian tiger mosquitoes are These ‘remedies’ have been debunked by Snopes.com. While liquid soap on a puddle of water might drown any mosquito which lands there, biting mosquitoes are attracted to the carbon dioxide we exhale and body warmth and would not be distracted by a dish of water and soap. Mosquitoes looking for water to lay eggs might be repelled by the presence of soap & seek another water source nearby. Listerine is not an insecticide nor a repellant. It will not hang in the air and kill mosquitoes as they fly through it, as an insecticide labeled for small flying insects would, and it will not reduce the mosquito population in your yard. The best way to help control mosquitoes in your neighborhood is to check weekly to ensure that you do not have any standing water on your property, including water in containers. Use an effective repellant if you will be exposed to biting mosquitoes. Remember to check your yard for any containers holding water—and tip them over! Attracting bats and purple martins to your yard is a good thing but they will not reduce your mosquito population. A bat seeking prey, usually a moth or beetle active during the daytime, martins still preferentially feed on much larger insects. Bug Zappers While people find it comforting to hear a bug zapper’s noise, they mostly kill moths and beetles. They also kill a number of species of beneficial insects, but less than seven percent of their kill is mosquitoes. Citrosa Plants These plants are scented geraniums engineered to add citronella oil. To be effective, the leaves would have to be crushed continuously. Because of this, they will not help repel mosquitoes from your yard. Listerine, Lemon Joy Inside this issue: Mosquito Trapping Mosquito Life Cycle 2 2 Why Do 2 Mosquitoes Bite? Midges—The Great Imposter 3 Repellants—Which is Best? Repeated studies have shown that DEET is the only repellant which consistently blocks mosquitoes from biting over extended time periods. There are two new repellants on the market, picaridin and oil of lemon eucalyptus. These two have been shown to repel mosquitoes, but neither one lasts as long as DEET so they cannot provide the same level of protection. In keeping with the story above, there are several household items which, rumor has it, can be used to repel mosquitoes. Dryer sheets, Vaporub and even banana peels have been touted as repellants. None have been proven in studies to have any repellant properties. P a g e 2 Surveillance—Mosquito Trapping So… how do we decide when a community needs to be sprayed? Our two types of adult mosquito surveillance are: landing rate counts (see Issue 1) and trapping. We use several kinds of mosquito traps in Maryland. The light trap, or CDC trap (named for Centers for Disease Control and Prevention) is small, portable and attracts mosquitoes with a small light bulb. Mosquitoes come to the light and are pulled down into our collection bag through a fan. This trap is hung from a tree branch and left overnight. Some areas of Maryland use dry ice (CO2, a major attractant for mosquitoes) alongside the trap as bait. The BG trap is our only trap frequented by Asian tiger mosquitoes, one of our peskiest species. It is about two feet tall and resembles a Chinese lantern. It sits on the ground and uses octenol and CO2 as attractants. Again, a fan sucks the mosquitoes into a bag and they are collected the next morning. The gravid trap is useful for disease surveillance, since it attracts female mosquitoes that have fed on blood and are ready to lay eggs. This trap uses very putrid water in a pan as an attractant—the fouler the better for egglaying! These traps may be left in one place all season, with someone coming to pick up the collections and add more water or replace the battery. All collections are brought back to the mosquito control office where the mosquitoes are identified to species. Some of these will be sent to the Maryland Department of Health and Mental Hygiene for disease testing. The thresholds used for these traps is the same: 12 females in an unbaited trap, 24 females in a baited trap overnight. A Centers for Disease Control and Prevention trap baited with dry ice. At right, a gravid trap, complete with stinky water A POEM Mosquitoes come to you to feed A little blood is all they need They’ll take it from your nice bare legs Then find a place to lay their eggs! At left is the mosquito life cycle—in the warmest part of the season, this cycle can be completed, from egg to adult, in only 5 days! A female mosquito taking blood—she feeds through her proboscis, her bayonet-like mouthparts So Why DO Mosquitoes Bite? Only female mosquitoes bite! The reason is simple—they need the protein in blood to develop their eggs. Once they’ve taken a full blood meal, they try to find either stagnant water or dry ground that has been flooded (and will be again) to lay their eggs. Different species have different egglaying habits. The eggs laid on the water surface will hatch within a day or so into very tiny larvae. Eggs laid on dry ground will wait for rains. When that site floods, the eggs hatch into larvae and continue their development. Larvae go through 4 instars, or sizes, as they eat, molt and grow. Once they’ve completed that 4th instar, they molt into the pupal stage (the equivalent of a cocoon in moths but much more active). They are only pupae for a day or two, and then emerge as adult mosquitoes to start the cycle all over again! M o s q u i t o N e w s Maryl and Depar tment of Maryland Department of Agriculture Martin O’Malley, Governor Anthony G. Brown, Lt. Governor Earl F. Hance, Secretary 50 Harry Truman Parkway Annapolis, MD 21401 Phone: 410-841-5870 Fax: 410-841-5734 Website: www.mda.state.md.us Cartoon courtesy of Fairfax County Health Dept. Don’t forget! Check your yard weekly to make sure you aren’t supplying the next batch of mosquitoes in your neighborhood. Remember: Tip it or Toss it! Check out our website: www.mda.state.md.us The Great Imposter: Chironomid Midges Midges are small flies, about ¼ inch in length, and are often confused with mosquitoes, which are similar in size and appearance. Midges are usually identified by their brushlike antenna. Midges also differ from mosquitoes in that they don’t bite or suck blood and are not involved in the transmission of disease. Midge larvae are small, worm-like, and may be blood red in color. The larvae feed on plankton and organic debris and develop in lakes, ponds, ditches, storm water retention sites, slow moving streams, river banks and highly polluted sewage water. The adults emerge late in the day, form swarms and are attracted to lights. Water front communities can be plagued for several weeks by massive swarms of adult midges. Due to the high numbers and the length of time over which the adults emerge, midges can affect the quality of life and have a negative impact on businesses, especially marinas and outdoor restaurants, in shore-front areas. Despite the trouble caused by midges, there are no state or local programs aimed at controlling them. Management Strategies . Reduce lighting around your house. Use less powerful bulbs and use yellow instead of white bulbs. . Reduce the amount of indoor lighting that shines through windows. Try to cover windows with blinds or curtains. . Delay turning lights on for as long as possible The midge, above, is lacking the proboscis, clearly seen on the mosquito’s head in the picture on the right.