Although it looks like an idea out of science fiction, giant mosquitoes exist. They wait for the dry season to pass to get out of their eggs, when the flooding provides the perfect environment for the larvae.
After Hurricane Florence, sightings of “giant mosquitoes” began to appear in North Carolina. What is happening with these mega mosquitoes that can be as big as a quarter of a dollar?
As a mosquito biologist, I am often asked to identify some species based on someone’s verbal report about these little bugs. In general, I can do pretty well if you give me descriptions like “I had striped legs and it was brown” or “It looked like something purple”.
What I’ve always fought with is when someone says “it was small” or “it was pretty big”. For the most part, size is not a good feature to identify the common mosquitoes that Americans find near their homes.
This is because relatively large or small mosquitoes can develop, depending on the conditions in which they grow: what entomologists call the larval environment . If the larval environment has few mosquitoes with which to compete, or is rich in nutrients, or has a cool temperature, the result is larger adult mosquitoes.
However, there are a couple of mosquito species that are truly gigantic. If someone says they saw a big mosquito and I continue with “big for a mosquito or too big to be a mosquito?” And they respond “too big to be a mosquito, but it was biting me”, then I know we really have a of a pair of “giant” mosquito species.
Under normal circumstances, these giant biting mosquitoes – known locally in North Carolina as “gallinippers” or scientifically as Psorophora ciliata or Psorophora howardi – are quite rare. They are two of the approximately 175 species of mosquitoes that we have in the United States. Its moment in the center of attention takes place after great floods , like those that we had with Hurricane Florence. These mosquitoes can be up to three times larger than their more typical cousins.
The gallinippers belong to a genus of mosquitoes that specialize in responding to floods. The females produce many eggs, which they deposit around areas that could be flooded, such as wet meadows, alluvial plains forests or even agricultural lands. These eggs are resistant to drying – which means they are not damaged in dry conditions – so they can expect the flood the following year, forming an “egg bank”. The eggs are fertilized as the female puts them, with sperm stored during mating. To obtain the blood needed to produce many eggs, these mosquitoes feed aggressively on mammals, and perhaps on other vertebrates from time to time.
But evolving to a giant size does not seem necessary to carry out these tasks. In fact, many other species of this genus are not giant, they are more typically the size of a “normal” mosquito. So, what about the gallinipper?
One possibility is the fact that gallinippers, like larvae, take advantage of other mosquito larvae. Perhaps its size is an adaptation to the consumption of other water mosquitoes produced by floods, which allows them to capture and consume more easily smaller species. The mosquitoes of more typical size that use these same waters are not predators. The giant size can also allow them to produce many more eggs, which can be an advantage when the floods arrive.
Gallinippers have a painful bite that is usually noticed by human victims, so the large numbers of these mosquitoes that appeared after Florence have received a lot of attention.
Being bitten by a giant mosquito may not seem like a big deal, and there are reasons to be calm. First, it is likely that these mosquitoes receive only a good dose of blood in their lives, which limits their ability to transmit a pathogen . For what the entomologists know, they do not transmit any pathogen to people. And since, like larvae, these giants eat other mosquitoes, maybe a big bite is worth 10 small ones? Finally, after the hurricane you can boast saying “I was bitten by a giant mosquito!”
Another good news is that adults are likely to live no more than a couple of weeks, so the big mosquito boom behind Florence is shrinking. Of course, now it seems that Hurricane Michael could trigger another round of gallinippers. Winter ends with the most immediate threat, but all those eggs are still there, waiting for next year’s floods.