As spring arrives, I cannot help but think about all of the organisms that will begin to emerge, hatch, or move north as the weather becomes more pleasant. This is a time for flowers to blossom, birds to migrate and begin singing again, and mosquitoes to emerge and complete their life cycle.
Mosquitoes are thought of mostly as a nuisance that will relentlessly follow and bite any vertebrate, which includes reptiles, amphibians, birds, some fish, and mammals, in search of a blood meal. They have ruined many a picnic, barbeque, or hike by their persistence in obtaining one. However, there is more to mosquitoes than just being a pest.
Mosquitoes are in a family of midge-like flies, Culicidae, and diverged from other flies approximately 260 million years ago. There are about 3,500 mosquito species that are known to science, and more to be identified and described. With this many species there is a huge amount of diversity, which includes species that are extremely well known and spread pathogens that cause disease, but also others that rarely interact with humans or other vertebrates.
Of the mosquito species that spread pathogens, not every species can spread the same pathogens. For instance, 30-40 species in the genus Anopheles (which contains 430 species) spread the parasite that causes malaria, but no other mosquito genus is known to carry this parasite. Species in the genus Culex are the primary carriers of the pathogens that cause West Nile virus, viral encephalitis, and filariasis. Species in the genus Aedes, such as the Asian tiger mosquito, carry pathogens that cause yellow fever, dengue, and viral encephalitis. Another aspect to consider is that even if a mosquito species that is known to carry a particular pathogen is present in a region, it will not carry or pass on that pathogen if that pathogen is not present in the environment as well. So although there are Anopheles species in the United States, you do not hear of people becoming infected with the parasite that causes malaria.
Not all species of mosquitoes suck blood. Of the species that do suck blood, it is only the female mosquitoes that have the mouth parts required to suck the blood of vertebrates. They do this so they have the nutrients and protein needed for egg production. Otherwise, both males and females feed on nectar and other plant sugars. Also, an interesting tidbit I found out is that in many species, the male mosquito has elaborate feathery looking antennae. They range from very small and not very obvious, to large and very elaborate. I recently saw a male mosquito resting on the windshield of my car. I am not good enough at identification to know what species, but I was proud that I could tell it was a male mosquito. Their bushy antennae cannot be missed.[slideshow_deploy id=’386′]
Examples of the bushy antennae of a male mosquito. These are used to detect females in the area. This occurs through picking up on the humming frequency of the wing beats of a female mosquito.
The species that do not consume blood are less well known and not encountered by humans as often. One example is a species in the genus Toxorhynchites. Commonly known as the elephant mosquito, these mosquitoes are the largest known and, as adults, their diet consists of saps and juices from plants, fruits, and also nectar. The larvae of mosquitoes in the genus Toxorhynchites are voracious aquatic predators and will frequently feed on the larvae of other, smaller, mosquito species.
This is just one example of a species that do not need a blood meal, but there are others. Although there are 3,500 species known to science, only a few hundred bite or bother humans. That still leaves a few thousand mosquito species that do not bite or bother humans, that either bite other vertebrate species, or do not bite any other species. All mosquitoes provide something to the environment in which they live, whether it is a food source, influencing the migration of caribou, or through acting as pollinators.
Severson, D. W., and Susanta K. Behura. 2012. Mosquito Genomics: Progress and Challenges. Annu. Rev. Entomol. 57: 143-66.
Fang, Janet. 2010. A world without mosquitoes. Nature. 466: 432-434.