Tiger Mosquito (Aedes albopictus)
This Southeast Asia native gets its vivid common name as a voracious all-day biter with distinctive stripes. Like all mosquitos, only females have the equipment to bite, the proboscis that male mosquitos lack. They “feed” on the blood of an animal host to get protein needed to produce eggs, so blood “meals” are a reproductive strategy, not nutrition. Mosquitos eat nectar from flowering plants, which means they are pollinators! Good to know—as you swat them.
Tiger mosquitos were first noted in the U.S. in Texas in 1988. Within 10 years, according to the CDC, this species was active in nearly 680 counties in 25 states. Documentation of their original spread from southern and California port areas into regions along interstate highways suggests that global container shipping was the travel agent for this (and other) tropical mosquito species to colonize temperate zones.
In fact, tiger mosquito females lay eggs on the sides of containers, just above a water line. Dehydrated eggs can stay viable for up to eight months! Eggs hatch when water rises, helping juicy new larvae survive in surface-feeding predators. Buckets, plant saucers, clogged gutters and your dog’s abandoned frisbee are all excellent breeding sites. One small grace from this habitat preference: Aedes albopictus is unlikely to reproduce in your yard’s soggy soil, so removing or inverting containers is a prime control for tiger mosquitos.
Also called the forest mosquito, Aedes albopictus lives outdoors as what’s called a cafeteria feeder, thriving on animal or human prey. This mixed-meal existence makes this species the least competent vector of diseases most effectively transmitted by its cousin, Aedes aegypti, an exclusively human-feeding, indoor dwelling and similarly striped fellow invader. St. Louis public health officials are on the lookout for A. aegypti, spreading north from ports of entry but not here yet.
Both these Aedes species are small, about ¼″ long, and vividly black and white, but it’s easy to tell them apart: A. albopictus has one white stripe along its head and back; an A. aegypti head and back will be marked with a white lyre, the shape of a small harp. These mosquitos can transmit Zika Virus, Chikungunya and Dengue Fever, serious health concerns that necessitate a serious and ecological response.
Adult tiger mosquitos are active all day. Other species that can’t tolerate midday heat only feed at dusk and dawn, the times we’ve been traditionally told to stay indoors for mosquito bite protection—and when municipalities tend to do chemical fogging. Tiger mosquitos are here to stay, so we need to adapt our strategies. This includes understanding that fogging only affects flying adult mosquitos; fogging has NO EFFECT on aquatic mosquito breeding, as it pumps out death to beneficial insects. Money and lives are wasted.
Culicidae, the mosquito family, has over 3,500 unique species, but only a couple of species in three genera—Aedes, Culex and Anopheles—can be vectors of human diseases. Dragonflies, bats, birds, fish and amphibians all eat mosquitos, making them crucial food web contributors. Taxonomists classify them within Diptera (“two-winged”), the fourth-largest order of insects which includes all true flies. Dipterans’ membranous front wings are their aerodynamic surfaces; hind wings of bugs in this order have evolved to be small, club-shaped structures called halteres that vibrate during flight, working like a gyroscope to help the insect’s balance.
Tiger mosquitos don’t fly far from their breeding site, only about 300 feet. They can live in this kind of limited range because they have a diverse range of prey. Like most mosquitos, they are weak flyers. You won’t find them biting on a windy day. Use this limitation to your advantage: plug in one or more electric fans around outdoor seating areas to be refreshed by their breezes while your gathering stays mosquito-free.
All Dipteran larvae are aquatic, and all mosquitos need standing, stagnant water to progress eggs through their larval and pupal stages. They become terrestrial, flying insects for their brief time as adults. Males live to mate, only 3–5 days. Tiger mosquito females can live for 4–6 weeks and lay over 100 eggs at a time through multiple breeding cycles. After blood feeding, a female will rest for a few days to digest and develop eggs.
Most mosquitos morph from egg to adult in 7–12 days. This cycle accelerates to 3-5 days in very hot weather, 90s and up. All larvae feed on decomposing plant matter and microorganisms as they grow through four instars. These “wigglers” are easy to spot—and dump!
When you can’t eliminate standing water, you can treat it with Bti (Bacillus thuringiensis israelensis), a bacterium that occurs naturally in soil spores. It’s not synthetic and it only affects dipterons. Widely available and affordably sold as Mosquito Dunks, this stuff changes water chemistry, so mosquito larvae guts explode. Literally. Nature is so cool.
Aedes albopictus shares an extraordinary range of sensory capacities with all mosquitos, including primary attraction to a blood meal host by the CO2 exhaled by all vertebrates. As a species that may feed on humans, the tiger mosquito then detects the long red-orange light wavelengths emitted by human skin, regardless of skin pigmentation. From a distance, mosquitoes are visually attracted by dark colors; hence our “light colored clothing” guidance during mosquito season. Fragrance attracts them too, so summer is a good time to go fragrance-free with products like detergent and body wash. Hygrosensation guides a female toward the humidity of standing water. In a typical yard or park with multiple species, sex pheromones help a mosquito find a con-specific mate.
Technically, mosquito repellants work by blocking some of the sensory cues the insect uses to find the body chemistry of preferred blood-meal prey, or because mosquitos dislike their odor. In practice, spraying on a repellant is like wrapping yourself in an Invisibility Cloak.
U.S. EPA now recognizes eight repellant ingredients as being safe and effective, including Catnip and Citronella Oils and Oil of Lemon Eucalyptus alongside DEET and other synthetics. We all emit CO2, but because body chemistry varies from person to person, and can change as we go through life, it’s useful to test repellants and keep a few kinds on hand. Plant-based DEET-free products are now readily available. Find a formula that works for you and use it!
Our region’s longer, hotter summers and shorter, milder winters mean that climate change gives tiger mosquitos (and their kin) a long warm welcome. Here’s how you can chill their impacts:
- Wear loose, light-colored clothing when working outdoors. Long pants, long sleeves.
- Use mosquito repellant! Keep a basket of several kinds on hand for summer play and gatherings.
- Plug in an electric fan when sitting outdoors. Fan breeze will keep mosquitos off—and keep you cool!
- Find, dump and remove containers around your property to eliminate the standing water mosquitos need to breed. Treat water you can’t remove with Mosquito Dunks.
- DON’T resort to chemical fogging! Bug spray kills bugs, period. Don’t fall prey to advertising claims, fogging WILL harm pollinators.
- Educate your local officials about ecological mosquito control. Talk with your neighbors too.
- Garden with native plants to attract and support a variety of mosquito predators. Biodiversity is Nature’s tried and true mosquito population control.
- Join the Citizen Science project, Mosquito Alert STL, to help local public health agencies monitor and responsibly respond to mosquito activity.
Learn more at www.mobot.org/MosquitoAlertSTL.
—Jean Ponzi
Green Resources Specialist, EarthWays Center of Missouri Botanical Garden