Mosquitoes on Maui

As you spend your days exploring Maui, you are likely to experience a couple of notable distractions from the native sights and sounds of the island: buzzing and biting from invasive mosquitoes. On Maui these insects are more than just an outdoor nuisance—they are causing catastrophic damage to the island’s ecosystems.

Types of Mosquitoes on Maui

The State of Hawai’i is home to eight invasive species of mosquitoes - six that bite humans and two that feed solely on plants. Of the species that bite, two are most common on Maui and can be categorized as day-biters or night-biters.

Day-Biters on Maui

Asian Tiger Mosquito (Aedes albopictus)

The Asian tiger mosquito will breed wherever there is clean, standing water. This includes natural and human-created sources. When you think of mosquitoes on Maui, it’s likely that you’re picturing this species.

When you are out hiking or playing in the backyard during the day and hear that annoying buzz in your ear, the black-and-white striped Aedes albopictus is the probable culprit. These mosquitoes will also bite near dusk and dawn, but rarely at night. That is when the next mosquito species begins to buzz and bite.

Night-Biters on Maui

Southern House Mosquito (Culex quinquefasciatus)

The southern house mosquito likes to breed in areas with wet, decomposing natural materials. Just like the Asian tiger mosquito, it will also breed in all types of human-created water sources (clogged gutters, tires, cans, and bottles), but it’s not as tied to human habitats.

This mosquito is the most common night-biter throughout Hawai’i and is typically at fault if you are bit at night while camping or spending time on the patio or lānai.

How Did They Get Here and Why Did They Stay?

Haleakalā National Park Forest Bird Biologist Chris Warren says, “Although mosquitoes are common throughout the world, Hawaiʻi's isolation meant that the archipelago was among the few places on the planet without mosquitoes.” A whaling vessel first brought mosquitoes to Hawaiʻi in 1826 and because of the favorable tropical climate, their populations thrived and expanded across the islands. “The introduction of mosquitoes happened less than 200 years ago,” Warren says, “just a blink in the eye of evolutionary history.” However, within that short period of time, climate change has caused the temperatures in Hawaiʻi to rise, allowing mosquito populations to migrate into new areas including high elevation forests that were previously too cool for mosquitoes to breed. The changing climate is now enabling mosquitoes to rapidly spread disease to vulnerable bird populations island-wide.

Mosquito Reproduction & Life Cycle

Mosquitoes reproduce sexually, meaning they require an egg and sperm to create offspring.

The female mosquito stores the male’s sperm in storage organs for her entire life. When she is ready, she coordinates the release of the sperm with her ovulation. The sperm and egg come together, share genetic information, and create a fertilized egg. The female mosquito then lays the fertilized eggs in or near water.

The mosquito life cycle consists of four stages: egg, larva, pupa, and adult. Once in water, eggs will hatch into larvae. After several days or weeks, larvae will develop into pupae (picture a caterpillar becoming a chrysalis). From the pupa, the adult stage mosquito emerges several days later. This cycle can take anywhere from two to four weeks, however in higher temperatures, an entire life cycle can happen in as little as one week. This shorter life cycle directly leads to larger populations of mosquitoes.

Ecological Impacts of Mosquitoes on Maui

In their native ranges, mosquitoes can be a beneficial part of an ecosystem as food sources or plant pollinators. But in Hawaiʻi, mosquitoes serve no ecological benefit.

The southern house mosquito, the first species of mosquito introduced to the islands, is the mosquito that is currently causing the most damage to the Hawaiʻi’s ecosystems. This mosquito is pushing Maui’s native forest birds closer to extinction each year by spreading avian malaria, a deadly disease caused by a blood parasite. Avian malaria is the main cause of population declines among the island’s forest bird populations.

“Many of our native birds evolved in isolation for millions of years and now their very existence is threatened by mosquitoes. These birds are already proven survivors—weathering a hurricane of human-caused threats (habitat loss, mammalian predators), but they are at the end of their rope with mosquitoes and avian malaria.” - Chris Warren, Forest Bird Biologist, Haleakalā National Park

As the forest birds have little or no ability to fight off mosquito-borne diseases, like malaria, four species of these birds are predicted to go extinct within the next two to ten years, with several other species not far behind.

Mosquito Management Efforts

All mosquitoes are invasive, non-native species in the Hawaiian Islands. Although a nuisance to people and animals, it is the mosquito’s destructive ecological effects that warrant the need for population suppression. Warren explains that in the past Hawaiʻi’s isolation meant that, “new species arrived in Hawaiʻi so infrequently (about one new species every 10,000 years), evolution had time to incorporate those new organisms without throwing the entire ecosystem out of whack.” But now, “new species are introduced at a rate of around one per month.” Environmental changes are now occurring faster than the native ecosystems can adapt.

Without intervention, Hawaiʻi’s diverse species, including Maui’s native forest birds, could be lost forever. Warren goes on to say that “even if we cannot stop all the new invaders, we can address the impacts of the most destructive species that are already here and give a leg up for the native Hawaiian species.”

This is why the National Park Service, in partnership with the State of Hawaiʻi and other agencies, is looking to manage Maui’s mosquito population.

In the past, the most common mosquito management technique was to use pesticides or alter habitats to remove breeding habitat. Many of these pesticides are often non-targeted and need to be applied across huge areas and are not considered an acceptable tool in this case. Removal of mosquito breeding habitat also often comes at the expense of the loss of habitat for numerous other species, including native invertebrates.

The National Park Service is looking to use a new method of mosquito management that focuses on stopping mosquitoes from ever getting the chance to bite or spread disease. This method, called the Incompatible Insect Technique (IIT), will ensure that female mosquitoes lay eggs that will never hatch.

The IIT method relies on Wolbachia, a naturally-occurring bacteria that lives only within the cells of insects, including the southern house mosquitoes on Maui, and some other arthropods. Scientists discovered that mosquitoes with different strains of Wolbachia are unable to reproduce with each other. Taking advantage of this, IIT involves raising male mosquitoes (which do not bite) in a lab with one strain of Wolbachia and releasing them into an area with mosquitoes with a different strain. When the wild females find and mate with these lab mosquitoes, their Wolbachia doesn’t match and none of her eggs hatch.

Native species in Hawai'i deserve a chance to evolve with their changing ecosystems and need protection now more than ever.

Conclusion

The mosquitoes that currently call Maui home are not supposed to be there. Since their introduction, they have fed on Maui’s forest birds, spreading the deadly disease of avian malaria. Rising temperatures from climate change have expanded the range of the southern house mosquito and its impacts.

Without proper management, the mosquito population will continue to disrupt the ecological balance of the island and within the next decade, will cause the extinction of several of Maui’s remaining native forest birds.

Learn more about the declining population of the Honeycreepers and what we can do to save them.