History
Mosquitoes have plagued humans since prehistoric times, perhaps for four
million years or more. Adult
mosquitoes have been found embedded in amber (fossilized resins)
from the Cretaceous and Jurassic periods, some with the blood meal
still intact. Although
they lived very long ago, those specimens are remarkably similar
to the mosquitoes of today.
Throughout history, human actions or inactions have been influenced by the presence of mosquitoes. For example, Roman legions were often forced to cut short their daily marches to build fortified encampments, complete with encircling smudge fires to ward off the hoards of mosquitoes that attacked at sundown. Later, efforts of the French to complete a canal across the isthmus of Central America were unsuccessful due to yellow fever and malaria epidemics in that region. The Panama Canal would not have been completed if the United States had not developed anti-mosquito campaigns to accompany the construction of that great project. Nevertheless, it cost dearly in lives of many workers to these mosquito-borne diseases.
Even the United States mainland has not escaped the devastation wrought by these ubiquitous pests. Notably, completion of the Tennessee Valley Flood Control Project and colonization of the everglades in Florida and the bayous in Louisiana would have been unattainable without some form of organized mosquito control.
Surprisingly, throughout history more individuals have died from mosquito-borne diseases than from any other single cause of mortality, including wars and famine. Even now, malaria continues to be the leading cause of mortality in many third world countries, causing over two million deaths among 270 million new cases annually.
There are approximately 3,500 species of mosquitoes distributed worldwide. Most, but not all, are capable of feeding upon humans and domestic animals, although they may not always prefer to do so. Many feed upon birds, wild animals or reptiles. In any one locality, relatively few species occur in numbers sufficient enough to create problems. For example, 53 mosquito species occur in California, but less than two dozen are considered important to human health and comfort.
Biology
Mosquitoes have four different stages of their life cycle- egg, larva,
pupa, and adult. During each stage of their life cycle, the mosquito
looks distinctly different than any other life stage. The mosquito
egg can develop into an adult mosquito within one week.
Eggs
The most common mosquitoes lay egg rafts that float on the water. Each raft contains from 100 to 400 eggs. Within a few days the eggs hatch into larva.
Larva
The
larva or “wiggler” comes to the surface to breathe through a
tube called a siphon. It sheds its skin or molts four times during the
next several days. It grows rapidly between each molt. On the fourth
molt it changes into a pupa. To see a video of larvae in a flower saucer,click
here.
Pupa
The pupa or “tumbler” cannot eat. It breathes through two tubes on its back. The adult mosquito grows inside the pupa and in two days or so, when it is fully developed, it splits the pupal skin and emerges to complete the life cycle or metamorphosis of the mosquito.
Adult
The newly emerged adult rests on the surface of the water until it is strong enough to fly away and feed.
For a diagram of the mosquito's life cycle, click here.
There are some insects that look very similar to mosquitoes. To see a list of these insects click here.
Diseases
As well as being a pest, mosquitoes can carry numerous diseases that can make people and animals sick.
West Nile Virus
The disease that is of most concern right now in Southern California is West Nile virus (WNV). West Nile virus has been in the United States since 1999 and in California since 2003. West Nile virus is spread to humans by mosquito bite. WNV is a blood-borne disease; there have not been any cases of a person contracting the virus through everyday contact with infected individuals. Although, there are records of people contracting the disease through organ transplants and blood transfusions. There are three different gradations of WNV: West Nile virus, West Nile fever and West Nile neuroinvasive disease. Most of the public who contract WNV (about 80%) will never show any symptoms; this gradation of the virus is referred to as West Nile virus. About 20% of the population that contracts the virus will contract West Nile fever. Symptoms of this include fever, headache, nausea, possible rash. These symptoms are very similar to flu- like symptoms and many people who contract West Nile fever think they have the flu. The more severe cases of West Nile are the neuroinvasive diseases. These can include encephalitis, meningitis and mengioencephalitis. This gradation of the virus can lead to stroke-like symptoms, coma, paralysis and even death. About 1% of the population that contracts WN will get these more severe symptoms. Click here for more information on West Nile virus.
Encephalitis
There are three forms of viral encephalitis transmitted by mosquitoes in Orange County: West Nile, St. Louis and Western Equine. All are carried by wild birds, most of which show no symptoms. Infected birds are then bitten by local mosquitoes that can pass the virus on to humans through future bites. Symptoms of encephalitis range from mild flu-like illness to severe brain inflammation that can cause death. West Nile virus and Western Equine encephalitis can affect horses and other animals as well as humans.
Malaria
Malaria is much less likely to occur in Orange County due to the necessity for human reservoirs of the disease. Anopheles mosquitoes, the vectors of malaria, are found in some areas of California, and there have been isolated instances where human reservoirs from other countries temporarily provided a source of malaria infection to local residents.
Find out more on what you can to control mosquitoes [What you can do]
Find out more about what OCVCD does to control mosquitoes [What We Do]
MOSQUITOES
