Mosquitoes

Overview:

In much of the world, including the United States, mosquitoes are a major public health problem capable of spreading several types of encephalitis, dog heartworm, malaria and others. Minnesota is famous for our mosquitoes. Some people call them our state bird. There are several diseases of potential concern to Minnesota public, horses, pets and other mammals. These include West Nile virus, LaCrosse encephalitis, western equine encephalitis, eastern equine encephalitis, St. Louis encephalitis and malaria. Unluckily, both night and day biting mosquitoes are common in Minnesota. Moreover, neither the mosquitoes nor the diseases they may transmit seek permission to enter our boundaries. Therefore, all of us are in charge to share the responsibility for managing these unpleasant human-biters and disease carriers.

Facts:

• Mosquito fossils date back at least as far as 100 million years ago.
• A female mosquito doesn't actually bite, but it stabs by piercing its proboscis, which is a tubular appendage.
• An adult female mosquito consumes about 0.000 017 ounce in a single blood meal.
• Depending of the species, a mosquito wing beats from 300 to 600 times per second.
• Male mosquitoes find female mosquitoes by listening to the sound of their wings beating. The males can actually identify the correct species by the pitch of the female's wings.
• Citronella does not repel mosquitoes through its smell. Mosquitoes dislike citronella because it irritates its feet.
• Every year, mosquitoes are responsible causing almost two million human deaths worldwide. This by transmitting diseases such as the West Nile virus, malaria, and Dengue fever. Second to this is the tsetse fly, which kills about 66,000 people annually.
• Like humans, mosquitoes have food preferences-not all mosquito species bite humans, some prefer birds, horses, frogs or turtles.

Identification:

• Mosquitoes have a pair of scaled wings, a pair of halteres (balance organs), a slender body, and long legs.
• The antenna is plumose in the males and pilose in the females.
• They have piercing and sucking mouthparts.
• Mosquito eggs are elongated, about 1/40 inch in length, and are dark brown or black when ready to hatch. Mosquito eggs may be laid singly or in a raft, depending on the species; i.e., the eggs of the mosquito species Culex tarsalis are laid in a raft formation in water.
• Larvae often called "wrigglers," look like hairy maggots with siphons. They twist and wriggle just below the water surface.
• The pupa has a comma-shaped body divisible into two distinct regions.  It is lighter than water and therefore floats at the surface.
• There are over 3500 identified species of mosquitoes throughout the world.
• Currently, there are 170 species in North America and about 50 species of mosquitoes are found in Minnesota.
• Mosquitoes are grouped into 41 genera. There are three genera of medical importance: Culex, Aedes and Anopheles.

Biology:

• Mosquitoes go through a complete metamorphosis life cycle and contain four separate and distinct stages: egg, larva, pupa, and adult.
• At each blood meal, a mosquito female lays its eggs in or around standing water.
• Eggs are laid one at a time and they float on the surface of the water. In the case of Culex and Culiseta species, the eggs are stuck together in rafts from 200- 300 eggs. A raft of eggs floats on the water and is about 1/4 inch long and 1/8 inch wide. Anopheles and Aedes species do not make egg rafts but lay their eggs separately in the water. Culex, Culiseta and Anopheles mosquitos lay their eggs on water; while Aedes species (floodwater mosquitoes), lay their eggs on damp soil that will be flooded by water.
• Depending on species, female mosquitoes may lay 100 to 300 eggs at a time and may average 1,000 to 3,000 during their lifespan.
• Eggs hatch within 24-48 hours. However, floodwater mosquito eggs hatch as soon as they are flooded, and can survive without water for two years or more.
• Larvae are filter feeders. They feed on microorganisms, algae and organic matter in the water, and molt four times in about 7-10 days. At the fourth instar, larvae reach a length of almost 1/2 inch before developing into pupae. Most larvae have siphon tubes for breathing and hang from the water surface. With the exception of Anopheles species, larvae do not have a siphon and lay parallel to the water surface to get a supply of oxygen through a breathing opening.
• Mosquito pupae do not feed. They float at the surface of the water, but they are mobile and use a tumbling motion to escape predation or when disturbed. A pupa takes oxygen through two breathing tubes called "trumpets." Pupa stage lasts 24-48 hours.
• The newly emerging mosquito has to rest on the surface of the water for a few minutes to dry its wings before it can fly away.
• Male and female mosquitoes require carbohydrate sources (nectar, plant exudates or fruit juices) throughout their life to maintain energy for flying, mating, and seeking hosts for blood meals. Generally male mosquitoes emerge a few days before female mosquitoes. This gives the males a chance to mature before the females emerge. The males then use their feathery antennae to hear the wings of the newly emerged females. Each mosquito species has a different sound to its wings so the males can find females of the same species. After they mate the female will look for a blood meal to obtain extra protein to develop eggs.
• Some mosquito species overwinter as eggs laid by the last generation of females in late summer. The eggs are usually submerged under ice and hatch in spring when water temperatures rise.
• Other kinds of mosquitoes overwinter as adult females that mate in the fall, enter hibernation in animal burrows, hollow logs or basements and pass the winter in a state of torpor. In spring, when temperatures are above 50 °F, the females emerge from hibernation, feed on blood and lay the eggs that produce the next generation of adults.
• A limited number of mosquitoes overwinter in the larval stage, often buried in the mud of freshwater swamps. When temperatures rise in spring, these mosquitoes begin feeding, complete their immature growth and eventually emerge as adults to continue their kind.
• Male mosquitoes can only live 1-3 weeks. Females live much longer. Hibernating females may live as long as 5 months or more depending on the species and predator pressures.
• Depending on the species and temperature conditions, the mosquito life cycle from egg to adult last 4 to 14 days.

Feeding Habits:

• Mosquito adults feed on flower nectar, juices, and decaying matter for flight energy.
• In order to develop fertile eggs, only the females of most mosquito species feed on blood.
• The females of different species prefer different hosts.The larvae are filter feeders of organic particulates.

Breeding Places:

The larval and pupal stages can be found in a variety of aquatic habitats including:

• Potted plants with pans underneath that hold water are good breeding sites.
• Drainage ditches with emergent vegetation are big producers.
• Standing water in low grassy areas.
• Roof gutters plugged with leaves hold water and mosquito larvae.
• Trash or "spare parts" and neglected outdoor appliances have lots of breeding places.
• Old tires.
• Rain barrels
• Unused or poorly maintained pools
• Water-filled tree holes
• Flat roofs
• Boats on trailers
• Birdbaths, barbecue grills, ash trays and other small containers that hold water
• Adult hiding and resting places: Dark, poorly ventilated and humid places as well as along the edges of dense vegetation.

Activity:

Most mosquito species are active during twilight hours and at night (i.e., Culex mosquitoes). However, some species around the home are active during the day. For example, Aedes mosquitoes are painful and persistent biters, attacking during daylight hours. They do not enter dwellings, and they prefer to bite mammals, including humans.

Most mosquitoes remain within 1 mile of their breeding site. A few species, such as Aedes mosquitoes are strong fliers and may have a fly range up to 20 miles or more from their breeding sources.

Finding Host:

• By chemical signals: mosquitoes can sense carbon dioxide and lactic acid up to 100 feet (36 meters) away
• By sight (movement): mosquitoes can locate their hosts when they are 30 feet away by detecting infrared radiation emitted by their host's body temperature.
• By thermal signals: mosquitoes have thermal/heat receptors on the tip of their antennae. At 10 feet away from the host, these sensors can detect the heat sources of warm-blooded animals, and pick up temperature changes as small as 0.1°C.

Adulticides; Barrier and Resting Habitat Treatments:

Treatment with synthetic pyrethroid insecticide to any surface area that a mosquito would rest on, such as:

• Lower limbs of shade trees
• Shrubs
• Tall grass
• Shaded areas on and around buildings where mosquitoes congregate, such as under decks and along foundations.
• Flower beds
• Home exteriors
• Fences

Larvae Treatments:

One can treat the breeding habitat with larvicides (such as Bti- a microbial compound, methoprene- an insect growth regulator, oils, and monomolecular films) to standing water. This helps reduce the adult mosquito population in nearby areas before they emerge from the water. Larvicide application sites include:

• Storm drains
• Catch basins
• Roadside ditches
• Waste treatment holding ponds
• Golf course standing water

FAQ's:

"How many species of mosquitoes are there?"
About 3,000.

"How many species of mosquitoes are in Minnesota?"
About 50.

"What does a mosquito weigh?"
About 2 to 2.5 milligrams (for an Aedes aegypti).

"How much blood does a female mosquito drink per, er, serving?"
About 5-millionths of a liter (for an Aedes aegypti).

"How do mosquitoes find new hosts?"
By sight, thermal and chemical signals

"What are some things that mosquitoes eat?"
Mosquitoes eat plant nectars and juices, and decaying matter for energy to fly. Females also take a blood meal so they can make eggs.

"What is the tube that a mosquito eats through called?"
Proboscis. This tube is like a straw. Mosquitoes put the tube into their food and suck the food up through it.

"Should I let mosquitoes bite me?"
No.  Most mosquito bites will only make you itchy. But, some mosquitoes can carry germs that spread to you when they bite.  In Minnesota, the germs they can carry are West Nile virus (WNV) and eastern equine encephalitis virus (EEE or Triple E).  These viruses can make some people very sick, but you can avoid getting sick by preventing mosquito bites!

"How fast can a mosquito fly?"
An estimated 1 to 1.5 miles per hour.

"How far do certain mosquitoes fly?"
Salt marsh mosquitoes migrate 75 to 100 miles.

"How far away can a mosquito smell you or another host?"
Up to 100 feet.

"How fast does a mosquito beat its wings when it flies?"
From 300 to 600 times per second.

"Why does a film of oil on water kill mosquito larvae?"
Because the oil clogs up the snorkel that the larvae use to breathe.

"Why don't mosquitoes transmit HIV virus?"
Mosquitoes  do not transmit HIV virus that cause AIDS due a number of reasons:

1. Studies with HIV clearly show that the virus responsible for the AIDS infection is regarded as food to the mosquito and is digested along with the blood meal.
2. Mosquitoes Do Not Ingest Enough HIV Particles to Transmit AIDS by Contamination (an AIDS-free individual would have to be bitten by 10 million mosquitoes that had begun feeding on an AIDS carrier to receive a single unit of HIV from contaminated mosquito mouthparts).
3. Most people have heard that mosquitoes regurgitate saliva before they feed, but are unaware that the food canal and salivary canal are separate passageways in the mosquito. The mosquito's feeding apparatus is an extremely complicated structure that is totally unlike the crude single-bore syringe. Unlike a syringe, the mosquito delivers salivary fluid through one passage and draws blood up another. As a result, the food canal is not flushed out like a used needle, and blood flow is always unidirectional. The mechanics involved in mosquito feeding are totally unlike the mechanisms employed by the drug user's needles. In short, mosquitoes are not flying hypodermic needles and a mosquito that disgorges saliva into your body is not flushing out the remnants of its last blood meal.

"Where is a place that I can find around my house where mosquitoes might lay their eggs?"
Female mosquitoes lay their eggs on or near water. They like any place water collects from puddles, birdbaths and old tires in your yard to swamps and ponds. You can help keep mosquitoes from laying eggs at your house by making sure your gutters are clean and removing water if it starts to collect anywhere.

"When do mosquitoes feed?"
Depending on the species, daytime, nighttime, and all times in-between.