Giving Thirst Traps a Whole New Meaning

Thirst Trap: An alluring or flirty photo meant to capture a viewer's attention.

What’s a mosquito trap? It’s like a thirst trap but it’s out in nature and not on Instagram!

Standard mosquito traps use lures to attract female mosquitoes to what they think is an inviting place to lay their eggs or a thirst-quenching blood meal. Female mosquitoes (the biters) look for a blood meal to help their eggs develop. But to inform future phases of this project, we needed to trap, collect, and monitor male mosquitoes, not females. Male mosquitoes do not bite and are not carriers of disease so fewer lures and traps have been developed to attract them. The mosquito researchers and technicians at Maui Forest Bird Recovery Project (MFBRP) have been working to adapt traditionally female-oriented traps to attract male mosquitoes.

Why attract and trap male mosquitoes, not females?

The mosquito control being implemented on Maui is a type of Incompatible Insect Technique (IIT) that will release Wolbachia-incompatible male southern house mosquitoes into wild breeding grounds to suppress the overall southern house mosquito population. (If that seems confusing, read our last article to understand the science behind IIT). To inform the small-scale releases, MFBRP had been working to trap wild male southern house mosquitoes to understand their current population numbers, where they fly, and which lures they are most attracted to. This information is vital to successfully implementing IIT.

Trapping to Understand the Current Population

Understanding the distribution and population sizes of wild male southern house mosquitoes helps determine how many incompatible males would need to be released in order to reduce the number of females at a site and to out-compete wild males for mating with the females. The more Wolbachia-incompatible male mosquitoes that are released at a location, the higher their chance of successful mating with wild females, which leads to a higher likelihood of non-viable eggs being laid (non-viable means the eggs won’t hatch). Releasing too many males at a location will not have negative ecological impacts, however, releasing them in the most efficient locations helps us make the best use of our time and male mosquito resources.

Trapping to Learn What Lures Attract Male Southern House Mosquitoes

Currently, three different types of lures are being used: CO2, “stinky” lure, and floral. Some traps use only one type of lure and some traps use combinations of different lures. Click to learn more about each type of lure.

Photograph of a mosquito trap connected to its battery source.

© Birds, Not Mosquitoes Photo

​CO2 lures release small amounts of CO2 into the air (approximately the same amount that each of us exhales). Initially used to attract female mosquitoes to a potential blood meal, this lure can attract males because where females go…males can follow!

“Stinky” lures use a mixture of organic compounds with a pungent, stinky smell similar to those found in human skin odors. This smell attracts some mosquito species of both sexes.

Floral lures use a flowery smell to attract mosquitoes. Male mosquitoes only eat nectar so they may be attracted to this lure.

From the research conducted with the different lures, MFBRP has found male mosquitoes in both the CO2 + stinky lure and stinky lure-only traps. However, the catch numbers were too low to accurately reflect male mosquito preferences. Future trapping efforts for the Wolbachia-incompatible male mosquitoes will exclude the use of floral lures to only research CO2 and a "stinky" lure vs. just stinky lure effectiveness.

Trapping to Inform Landscape Scale Releases

Research from these traps informed the next phase of this project: small-scale releases of the Wolbachia-incompatible male mosquitoes in the high-elevation forests on the slopes of Haleakalā, Maui. Now, the traps will be vital in catching the released male mosquitoes to help guide management and decisions for the IIT project. Small-scale pilot releases of Wolbachia-incompatible male mosquitoes started in mid-May after the Finding of No Significant Impact for the East Maui Environmental Assessment. These pilot releases will also inform the larger landscape use of this mosquito control technique on Maui.

It Takes a Crew!

It’s no small feat to set and continuously run mosquito traps. On the first day of a trapping session, crews go out in the evening to turn on the traps and each morning they go back out tocollect each trap’s overnight catch and data. Overnight data is the most important because southern house mosquitoes are most active at night, dawn, and dusk.

During the morning shift, field technicians go out to each trap to manually take measurements of the trap function, collect the small netted bags attached to each trap (which may contain mosquitoes), and change the trap battery if needed.

Back at the office, the bags containing suspected mosquitoes are frozen to ensure that the insects are immobilized for identification. Later, a field technician trained in mosquito identification examines the contents. Ideally, male southern house mosquitoes are captured, but sometimes other insects like moths, midges, flies, and other mosquito species are attracted to the lures and are caught in the trap. They take notes on the bag contents–even if no mosquitoes are present. Not catching the target species is still important data! After some very careful sorting, the technician uploads the bag’s data into the project data set.

This routine continues day after day, collecting as much data as possible for the trapping session’s duration.

Mosquito control on Maui would not be possible without this dedicated and hard-working mosquito crew! Unfortunately, we don’t all have the privilege to work as mosquito crew technicians for MFBRP, but we can be part of a larger “mosquito crew” in our own neighborhoods and communities! Here are a few simple things we can each do to help eliminate mosquito breeding grounds and decrease invasive mosquito populations:

-Dump out standing water in buckets, wheelbarrows, and bins.

-Fix leaky faucets and hoses that are dripping water.

-Flush or dump out water from bromeliads and other leafy plants once a week.

-Clean out gutters so water can run freely.

-Clean up trash and debris; for example, dispose of old tires or anything that can hold water.

For more information about Birds, Not Mosquitoes and the use of IIT mosquito control in Hawaiʻi, visit our website at birdsnotmosquitoes.org.

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About Maui Forest Bird Recovery Project: Maui Forest Bird Recovery Project is a project of the Pacific Cooperative Studies Unit under the Research Corporation of the University of Hawaiʻi-Mānoa and is dedicated to developing and implementing techniques that recover Maui's endangered birds. They are a vital Birds, Not Mosquitoes partner providing expertise and technical support on Maui.