Why are there no mosquitoes in Hawaii?
Mosquitoes are common in most parts of the world. You probably think that Hawaii would be a good home for them, but it is not. Why?
The short answer is because they can’t survive in the climate there. But mosquitoes need more than warm weather to live and reproduce; many other factors contribute to their survival.
Weather, topography, and ocean currents combine to make Hawaii an improbable home for mosquitoes.
The climate in Hawaii is generally dry, and there is little standing water where mosquitoes could breed.
Mosquitoes need water to reproduce; they deposit their eggs on the surface of stagnant or still water, and those eggs later hatch into larvae that live at the bottom of the pool.
This is why it’s important to keep drains plugged in and remove things that collect water near your home, like old tires, buckets, planters, or toys.
Mosquitoes living in Hawaii lay their eggs in marine areas where they have easy access to saltwater.
Because the ground lines the shoreline with porous lava rock, freshwater cannot accumulate and form pools.
This means there is almost no standing freshwater, and the salty ocean limits the places where mosquito larvae can survive.
Furthermore, much of the island chain was formed from underwater volcanic eruptions, bringing salt to the surface in upwelling. The combination of dry weather and salinity keeps Honolulu free of mosquitoes.
Does Big Island have mosquitoes?
The Big Island also has no significant mosquito problems, but it does have a few mosquito species that can make life difficult for residents from time to time.
There is one type of Culex mosquito on the Big Island, which primarily breeds in puddles and small pools of water during the rainy season.
Sometimes these mosquitoes are so numerous in the southern part of the island that people abandon outdoor activities.
What about Oahu?
The most common mosquito on Oahu is Aedes vexans, which feeds primarily on birds but sometimes bites humans.
This mosquito breeds in slightly salty or brackish water, such as marshes or drainage ditches, and its larvae are not found in the freshwater bodies favored by Culex mosquitoes.
Like other Hawaiian islands, Oahu experiences a proliferation of mosquitoes after heavy rains.
However, the increased frequency of the island’s rainy spells is a relatively recent phenomenon.
Human activities have disrupted the local ecosystem so much that there are fewer small wetlands for Aedes vexans and other mosquito species to breed in than there once were.
As a result, the local mosquito populations grow more slowly after heavy rains than they used to.
What about Hawaii’s other islands?
Although the Big Island and Oahu have some mosquito problems, they’re not as bad as those on other Hawaiian islands.
That’s because each of the eight major Hawaiian islands is a separate biozone with its own climate. Although a few mosquitoes can survive on all of them, different species dominate on each one.
The mosquito swarms on many of Hawaii’s smaller islands are horrific. Mosquitoes on some of the smaller, uninhabited atolls are so numerous that they’ve driven away tourists who came to snorkel and sunbathe.
Even on inhabited islands, mosquito swarms can be enough to ruin picnics or barbecues. Some small towns have had to switch to spraying with trucks because the multitudes were so bad that hand sprayers couldn’t keep up.
What can be done about mosquitoes?
Although many people like to blame mosquito swarms on global warming, most authorities agree that this is inaccurate.
There are more mosquitoes in some places now than there used to be, but it’s because humans have created more habitats for mosquitoes.
For example, the draining of marshes and wetlands has increased the number of places where mosquito larvae can grow into adults.
What can be done to reduce the threat from mosquitoes?
People have successfully used swamp coolers or misters to keep mosquito numbers down around their homes in some areas.
In most cases, though, limiting their habitat is the only way to significantly reduce the number of mosquitoes. This can be done by eliminating standing water around homes and businesses.
A concerted effort to clean up Hawaii’s waterways could have a significant impact on its mosquito populations. The more raw sewage that gets into storm drains or directly into bodies of water, the more mosquito larvae will breed there.
What islands have no mosquitoes?
Although there are no mosquitoes on the Big Island, Oahu, and many of the smaller islands, one not insignificant exception are Niihau.
This small island west of Kauai is privately owned and called “The Forbidden Isle” because its access is highly restricted.
Niihau used to be completely closed off to outsiders, but in the 1950s, the owners began giving permission for occasional day visits.
Because of its private status, Niihau has few mosquitoes—or any other insects for that matter.
Are mosquitoes year-round in Hawaii?
Mosquitoes are present throughout Hawaii, but they are most numerous during the summer rainy season.
That’s not to say that mosquitoes can’t be a problem out of season.
They can be terrible after heavy rains because flooding brings mosquito larvae up from the soil of riverbanks and other wet areas.
What about the Asian Tiger Mosquito?
Although some native mosquito species are in Hawaii, the most potentially harmful is the Asian Tiger Mosquito.
Native to Southeast Asia, these species first arrived in Hawaii via infested freight containers and by travelers who didn’t know it was a carrier for dengue fever and other diseases.
This mosquito thrives in urban areas but spreads rapidly to the surrounding countryside as well.
Unlike some other mosquitoes that lay eggs in a single location and then move on, female Asian tiger mosquitoes bite several people and animals as well before they drop off their load of eggs. This means that new breeding sites can appear miles from an infestation’s origin.
To learn more about mosquitoes and the diseases they carry, visit the Asian Tiger Mosquito entry at Bug of the Week.