Mosquito Information

Larval and Adult Habits, Habitat, and Life Cycle

Generally speaking all mosquitoes possess the same habits with some slight variations depending on species. All mosquitoes need three main things to survive; stagnant water void of natural predators for rearing larvae, dense vegetation like trees and shrubs for resting habitat, and for the female mosquito, a blood meal in order to produce eggs.

Stagnant Water- When female mosquitoes lay eggs, they search for stagnant water that is void of natural predators. This is why it is highly unlikely to see mosquitoes emerge from a stream or pond. These types of waters are filled with natural predators, such as fish and dragonflies that eat mosquito larvae. Even wetlands and swamps can be real hit or miss when it comes to breeding mosquitoes. Some early spring mosquitoes are found breeding in these types of waters, but once the predators wake up from winter hibernation and reestablish themselves the mosquito larvae become vacant.

In general, female mosquitoes are looking for smaller intermittent water bodies to lay their eggs. Each species prefers different areas. For example, Asian Tiger mosquitoes prefer artificial containers like tires or buckets filled with water, while a Common House mosquito prefers a water filled retention pond or water with lots of organic matter. Some prefer natural containers such as tree holes and others prefer storm water catch basins. Often-times surveillance of breeding habitat is a good indication of what mosquito species are prevalent.

With all that said however one thing is certain. You can eliminate mosquito numbers by treating or removing stagnant water around your property.

retention pond

Retention Pond can produce thousands of mosquitoes each year if not properly monitoired

                                                                   

Dense Vegetation and Shrubs

Mosquitoes will dry out and die in the sun, therefore they must find places in the shade during the day. This is why you typically only get bothered by mosquitoes from dusk till dawn. One exception is the Asian Tiger Mosquito as they do bite in the daytime, but they will immediately retreat to shade once they have fed. Mosquitoes will often times use the underside of leaves of trees and shrubs to accommodate their shade need, and the denser the vegetation the better. Keeping your property trimmed and void of overgrown vines and weeds will help mitigate mosquito nuisances.

dense vegetation

Dense vegetation is great resting habitat for mosquitoes

Blood Meal

It may be surprising to learn some facts about mosquito feeding habits and their tendency to bite. First, both male and female mosquitoes largely feed on nectar but only female mosquitoes take a blood meal. The female mosquitoes must take a blood meal in order to get protein and amino acids needed to produce eggs. Once a female mosquito has taken a blood meal, she is what we call a gravid mosquito (mosquito that is ready to lay eggs after taking a blood meal). Secondly, not all mosquitoes look to humans for their main source of a blood meal. There are many different species of mosquitoes that will prefer to take a blood meal from an amphibian, reptile, bird, or small mammals over a human. Other mosquitoes, like the Asian Tiger Mosquito, will regularly bite humans and be quite a nuisance.

As a rule of thumb, mosquitoes will typically not travel far from water in which they were born, as long as they can find their three main sources that support their life. This is often why when you are being bothered by mosquitoes they are either coming from your property or very close by.

Life Cycle

A female mosquito will lay eggs in stagnant water. Some species lay single eggs while others lay egg rafts. From the eggs, mosquito larvae emerge and will go through 4 different growth changes stages called instars. After the fourth instar they will molt into what is called a pupa. Lastly, out of the pupa stage they will emerge into an adult mosquito. This total process can take anywhere from 8-18 days and is dependent on species, water temperature, and food availability.

larvae

Mosquito larvae caught from a small retention pond

West Nile Virus and Other Diseases 

West Nile Virus

West Nile Virus was first discovered in the United States in 1999 in New York City, and by 2000 the virus had made its way to Pennsylvania. West Nile Virus transfers to humans when an infected mosquito takes a blood meal from an infected bird and, then bites a human. This virus is the main mosquito-borne disease in Pennsylvania that is transmittable to humans.

Understanding the risk and the health issues associated with this virus is important. 80% of people who contract West Nile Virus are asymptomatic, meaning they show little to no symptoms, 20% develop West Nile Fever which produces flu like symptoms such as fever, joint pain, vomiting, diarrhea, and rash. Less than 1% of the people who contract West Nile Virus develop West Nile Encephalitis in which symptoms include; high fever, headache, neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, paralysis, and in rare cases death.

Beginning in the spring, the virus begins its amplification within the bird population. A mosquito will take a blood meal from a bird infected with the virus and then that mosquito will become infected. That same mosquito will eventually seek another avian blood meal, and this time the virus will be transmitted from mosquito to bird, and this virus cycle will continue to repeat itself, subsequently amplifying the virus in both mosquito and bird populations. Mosquitoes such as the Common House and White Dotted mosquito predominately seek blood meals from birds. These two types of mosquitoes are what are known as WNV amplifiers, meaning they increase the virus prevalence within the environment. The more abundant these two species of mosquitoes are, the higher the prevalence of the virus. This is why these two species of mosquitoes are the main target species for both testing and control.

While West Nile Virus mostly occurs in the mosquito and bird populations, it is sometimes transferred to humans or other mammals such as horses. As stated, the Common House and White Dotted Mosquito predominately bite birds, but it does not mean that they will not take a blood meal from a different host if need be. That same mosquito that has bitten a bird infected with the virus, may take a blood meal from a human, infecting he or she with virus. Humans are what are known as both incidental hosts and dead-end hosts, meaning we were not the intended host and that the virus cannot spread from us. It should also be noted that while the two mosquitoes mentioned are the main amplifiers and bridge vectors of the virus, there are other mosquito species, such as the Common Summer Mosquito (Culex salinarius)  that can carry and transmit the virus as well. The program typically starts getting its first positive pools of mosquitoes in July and will typically increase until abundant until October when mosquitoes become less active. Human cases increase in late summer/early fall because Culex species take blood meals from humans in order to obtain the necessary nutrients to overwinter.

 

Other Mosquito Borne Diseases in which to be Aware

Eastern Equine Encephalitis (Triple E)- Triple E is rare but has a 33% fatality rate in humans. Even if somebody survives Triple E they may have permanent neurological symptoms. The symptoms for this disease often mimic those of severe West Nile Virus. There have only been three human cases ever reported in Pennsylvania in 1968, 1979, and 2018. In 2019, four horses and six avian positives were reported in Pennsylvania. The main vectors of this virus are the Cattail (Coquillettidia perturbans) and Woodland Pool (Culiseta melanura) mosquitoes, which are not very populous in Franklin County. In 2019, out of the 46,000 mosquitoes caught 41 were Cattail mosquitoes and 48 were Woodland Pool mosquitoes.

Zika Virus- Zika Virus is another rare disease and mimics the same symptoms of West Nile Virus. Pennsylvania has only seen cases of Zika virus that were travel related and to date no local transmission from mosquito to human has been documented. Florida has had some local transmission cases, most notably in 2016 when there were 218 mosquito-borne cases. Although Pennsylvania has historically not had to worry about Zika virus, there is concern for several reasons. First, the main vector of this virus is the Asian Tiger Mosquito which is substantially populated in Franklin County. Secondly, this virus can cause microcephaly in babies in the womb of infected mothers. Third, unlike other mosquito-borne diseases Zika Virus can be transferred sexually. For these reasons, Zika is being closely watched.

Dengue and Chikungunya Virus- These two viruses are extremely rare, and all cases in Pennsylvania have been travel related. Some historic vector transmission cases have been found in south Texas and Florida. Like the other mosquito-borne diseases these viruses symptoms mimic West Nile Virus. The main vector species of these viruses is the Asian Tiger Mosquito.

 

Asian Tiger Mosquitoes

The Asian Tiger Mosquito is an invasive mosquito in Pennsylvania and Franklin County from the tropical areas of Southeast Asia. Their physical characteristics include being black and coloration, white stripes, with a white stripe running down its thorax, head and proboscis. They are also much smaller than other mosquitoes. Unlike many other species of mosquitoes, Asian Tigers will seek blood meals and bite during the day. These mosquitoes are extremely aggressive and will often be found in large quantities.

asian tiger mosquito up close

A close up of an Asian Tiger Mosquito

Asian Tiger Mosquitoes breed in artificial containers such as tires, kid’s pools, buckets, corrugated pipe, clogged rain gutters; anything that is outside that can collect rain water. Once they emerge they will seek dense vegetation to rest and the females will wait on a blood meal.

 

 

Habitat such as this water filled flower pot make excellent habitat for Asian Tiger Mosquito larvaeHabitat such as this water filled flower pot make excellent habitat for Asian Tiger Mosquito larvae

Asian Tiger Mosquitoes have a very short flight range, usually only traveling about 200 yards from where they are born. This is why if you are being bothered by these mosquitoes it is either your property or a neighboring property they are emerging from. Asian Tiger Mosquitoes were initially found predominantly within the boroughs of Franklin County because urban areas tend to have more artificial containers than suburban and rural areas. In recent years this species of mosquito has become more of a nuisance in suburban and rural areas. They are spreading around the county, and their numbers continue to rise.

In 2008, the first Asian Tiger mosquito was caught in a trap within the Chambersburg Borough. In 2019, traps were set at a total of 155 different sites throughout the county. Asian Tiger mosquitoes were caught at 78 of these sites (50%). Compare that to 2013 when traps were set at 177 different sites and only 32 of these sites caught Asian Tigers (18%). In just 6 short years these mosquitoes expanded their locations in Franklin County substantially. 

 

How to Control Mosquitoes Around Your Home and Property

If you are being bothered by mosquitoes around your home and property there is an extremely high likelihood that they are coming from your property or a neighboring one. The very first thing you need to do is to make sure you do not have any standing water around your home. Below is a list of places that can commonly hold water and breed mosquitoes around your home.

  • Puddles and flooded out areas in your yard
  • Tree holes
  • Tarps
  • Buckets
  • Clogged rain gutters or down spouts, corrugated pipe from downspout running uphill
  • Flower pots
  • Bird bath
  • Any artificial container that can hold water

 

hole with waterbuckettube

 

 

 

 

 

 

 

 

 

 

Stagnant water can be found in unexpected places.

Once you have identified areas around your home that could potentially breed mosquitoes you then need to know what to do about it. Any of the artificial containers holding water should be dumped and stored in a way as to no longer collect water. Gutters and downspouts should be cleaned out and corrugated pipe from the down spout should be running downhill not uphill. Bird bath water should be changed every five days at minimum. These are all simple fixes and will greatly reduce the number of mosquitoes around your home, but what about water that you can’t physically get rid of?

If you have low lying areas holding water, or tree holes holding water, obviously you cannot simply dump it. In this case you will need to use a larvicide product to kill the mosquito larvae. Products like Summit’s Mosquito Dunks are a great thing to use in these situations. They continue to work for 30 days and cover 100 square feet. You can also use Summit’s Mosquito Bits which last three weeks after application. Both of these products active ingredient is BTI and is non-toxic to humans and pets, but with any pesticide application it is important to read and follow label instructions.

mosquito donut dunk

Mosquito Dunks

Once you have identified and taken care of any mosquito larvae on your property, your next step is to be getting rid of any adult mosquitoes that have already hatched and remain. Summit makes a spray that you can hook up to your garden hose and spray down any dense vegetation like trees and shrubs around your property where mosquitoes hide. This product’s residual can last up to 4 weeks and its active ingerdient is permethrin. Like the larvacide products, it is important to read and follow label instructions so that you do not harm non-target species.

 

mosquito spray

Mosquito & Gnat Barrier Spray

 

Products to use and Ways to Protect Yourself Against Mosquito Bites

Deet- Research has shown that insect repellents containing DEET are effective at repelling mosquitoes. Like sunscreen, the higher percentage of DEET concentration, the longer time period the product will last. If you are going to be outside where mosquitoes are for an hour or two, you can use a lower concertation of DEET. If you expect to be out longer, use a higher concentration. It is important to note that DEET does not kill mosquitoes, it just repels them. DEET products used as directed should not be harmful to use on the skin and clothes, depending on the material of your clothing, as it can damage some clothing containing plastic materials.

Permethrin-The second option are products containing 0.5% permethrin. The most common product that contains this active ingredient is Sawyer, which is used to treat clothes, but should not be sprayed on skin. Clothes should be placed on an outside line, sprayed, and allowed to dry. The product works when the permethrin makes a strong bond with the fibers in the clothing, which can last up to 6 weeks or 6 washings. The permethrin not only deters mosquitoes from landing on you, but it also kills them if one were to come into contact with your clothes.

Natural Oils-The third option is a more natural approach to mosquito repellents. The CDC has recommendations of oils derived from plants shown to be effective in repelling and/or killing mosquitoes. There is still debate on the level of effectiveness of these natural oils when comparing it to DEET and permethrin. The oils the CDC recommends are: 2-undecanone, garlic oil, rosemary, cedar, peppermint, thyme, geraniol, nootkatone, and lemon eucalyptus.

Thermacell- A thermacell is a handheld device that creates mosquito protection around you. It is powered by butane which is used to heat up a pad that contains a repellent called allethrin. Allethrin is a synthetic copy of a natural repellent found in chrysanthemum. The repellent fills the air around you to create the mosquito barrier.

Long Sleeves and Pants- While mosquitoes can bite through clothing it is difficult for them to do so. Long sleeves and long pants can add an extra barrier between the mosquito and your skin.

Fan- If you enjoy sitting on your porch or yard during the summer but are being bothered by mosquitoes, you can always set up a fan to blow air across you. Mosquitoes are very weak flyers and they cannot fly against a stiff wind.

How the Public can Help

When new breeding sites emerge the public can make it known to the program so that the areas can be surveyed. Sharing information about standing water or high mosquito activity is encouraged. Citizens can report using our online app at https://planning-franklincountypa.hub.arcgis.com/pages/public-info or call or email Jason Goetz at jgoetz@franklincountypa.gov or 717-261-3855.