Pestworld Magazine Focusing on the Business of Pest Management
MOSQUITOES
I have always heard that mosquitos stop biting in the winter because the cold weather kills them off. If that is true, then how do they return again every spring?
The decline in biting mosquitoes during the colder months is mostly due to a lack of warmth, not because all of the mosquitoes are dead. Mosquitoes, like most insects, are ectothermic, meaning they cannot generate their own body heat. Instead, they rely on sunlight or other external sources for warmth. Mosquitoes require heat to power their flight muscles, which are needed to fly so they can find a meal or a mate. The warmer the air temperature, the more use mosquitoes have of their wings. As temperatures start to drop in fall, the lack of warmth causes flight muscles grow sluggish and mosquitoes eventually become inactive. Mosquitoes use the falling temperatures as a clue that winter is approaching, and prepare for the cold months to come. How mosquitoes survive the winter can differ from one species to the next. Some mosquitoes overwinter as adults by hiding in animal burrows, tree holes or other insulated shelters. Other species endure the cold in the egg stage. In late fall, the last generation of adult mosquitoes lay eggs that lie dormant through the winter months. Once air temperatures warm back up and rainfall increases, usually in early spring, the eggs are triggered to hatch and the next generation of mosquitoes emerges. A few species even overwinter as larvae, armed with special anti-freeze proteins in their hemolymph (insect blood) that protect them against sub-freezing temperatures. Understanding exactly how mosquitoes survive extreme temperatures helps to direct our seasonal management efforts, improving our ability to control these important pests.
What is the best way to protect myself from biting insects while working outdoors this summer?
Mosquitoes, ticks and other biting pests are more than just an itchy nuisance— they can even spread disease. So, protecting yourself from bug bites is an essential part of on-the-job safety. Here few things you can do to reduce your risk of being bitten when working outdoors. First, try to cover as much of your skin as possible with protective clothing such as a long-sleeved shirt, pants, socks and a hat. Mosquitoes and other biting flies are often attracted to darker colors, so choose lighter clothing if you have the option. Some clothing and protective gear even comes pre-treated with the repellant insecticide permethrin and can offer an added level of protection. For any skin that is not covered, the Centers for Disease Control recommends using EPA-registered insect repellents that contain at least 20 percent DEET, picaridin, oil of lemon eucalyptus, IR3535, or 2-undecanone. All of these repellants offer protection against mosquitoes, but products containing at least 20 percent DEET are most effective against mosquitoes, ticks and other biting pests. If you plan on using sunscreen, be sure to apply the sunscreen first and let it dry before applying the insect repellent. When using any insect repellent, always read and follow the label instructions before applying.
What mosquitoes are capable of transmitting Zika virus?
Zika fever, caused by the Zika virus, has been detected in every country in North and South America with the exception of Chile and Canada. The symptoms of the illness include fatigue, joint and back pain, fever, skin rash, headache and eye redness. Most people infected with Zika fever show no symptoms. Most alarming is the association between Zika infection in pregnant women and a certain birth defect in infants called microcephaly, or reduced head size due to incomplete brain development. Microcephaly can result in a range of problems in children including developmental delays and intellectual disabilities. It’s important to remember that mosquitoes are not the cause of Zika fever. Instead, certain mosquitoes are capable of transmitting the virus that causes the disease. Zika transmission is most commonly associated with the yellow fever mosquito (Aedes aegypti), but the Asian tiger mosquito (Aedes albopictus) is also believed to be a competent vector of the virus. Both of these mosquitoes are present in the United States and the Caribbean and are aggressive daytime biters. The distribution of the yellow fever mosquito is restricted to tropical and subtropical climates. In the United States, it is primarily found in the Southeast and Gulf states with pockets in the Southwest and California.
The Asian tiger mosquito, on the other hand, is better adapted to cooler climates and has a much wider distribution, ranging into coastal regions of the southern New England states and into the Midwest, Southwest and California. Both species are commonly associated with structures, specializing in breeding in man-made containers with very little water present (Asian tiger mosquito larvae have been observed developing in containers as small as bottle caps). In addition to residual treatment of adult mosquito resting sites, any potential breeding sites on a client’s property should be identified and eliminated; including clogged roof gutters and drainpipes leading from downspouts.
