Ten Things to Love About Mosquitoes
Yes, mosquitoes are the most dangerous animals on the planet. Thing is, they’re not all bad. In fact, there are relatively few of the 3,000 or so known mosquito species found throughout the world that actually have a significant impact on humans. The majority of mosquitoes aren’t involved in the spread of pathogens that cause dengue fever or malaria, the two diseases with the greatest impact on humans. In fact many are either incapable of transmitting pathogens or just don’t have a taste for humans so will never bite us. Detested by many, the diversity and beauty of mosquitoes is all too often overlooked.
Here are ten things to love about mosquitoes.
1. Mosquitoes have been sucking blood for a really long time. The oldest known mosquito specimen is of Burmaculex antiqus described from amber around 100–90 million years old. More recently, a fossilised mosquito with an engorged abdomen confirmed that blood feeding has been going on for at least 46 million years. Modern mosquitoes are happy to feed on alligators and other reptiles so there is little doubt that they had a taste for dinosaurs too. They’ve probably been plaguing humans throughout their evolution too. Perhaps our ancestors once used aromatic leaves (either crushed or smouldering) to protect themselves from nuisance-biting mozzies, something we’re still doing today.
2. No niche left unsettled. Mosquitoes need water, perhaps more than they need blood. The immature stages of mosquitoes (commonly called wrigglers (larvae) or tumblers (pupae)) need standing water to complete their development. Despite common urban myths, mosquitoes cannot complete their development in mud, long grass or in the leaves of trees. Where they find that water demonstrates an amazing ability to adapt. From highly saline coastal rock pools to polluted urban drains to pristine freshwater wetlands to alpine snowmelt pools, each mosquito has become intrinsically linked to particular environmental niche. We praise many other organisms for their ability to adapt, how about some love for mosquitoes? Let’s take just one example, the pitcher plant mosquito Wyeomyia smithii. This mosquito has adapted to life in a place most insects would probably avoid, the jaws of the “insectivorous” pitcher plant. The mosquito’s eggs are laid within the plant and larvae develop within the liquid stored within the leaves of the plant and feed on the corpses of other trapped and killed arthropods. Even more amazingly, the immature stages of this mosquito overwinters within the frozen liquid within the plant.
3. No blood, no problem. The majority of mosquitoes need blood. The female mosquitoes require the nutritional hit to help develop eggs. However, in some species, the need for blood to develop their first batch of eggs isn’t required. The phenomenon is known as “autogeny” and a range of species, from the crab hole inhabiting mosquito, Deinocerites cancer, to the Australian saltmarsh mosquito, Aedes vigilax, have been documented laying eggs based on stored nutritional reserves from their immature stages. However, given the chance to bite before eggs have been laid, these mosquitoes usually do. Most fascinating has been some recent research into the London underground mosquito, Culex pipiens f molestus, that demonstrated that the mosquito will forgo a blood meal, even when one is available, until after their first batch of eggs is laid.
4. Mosquitoes help out with mosquito control. The immature stages of some mosquito species are predatory, feeding on the immature stages of other mosquitoes (with the occasional bout of cannibalism thrown in for good measure). Some of these mosquitoes have been proposed as potential biological control agents. Immature mosquitoes belonging to the genus Toxorhynchites are predatory and this species is often nominated as an ideal candidate for mosquito control as the adult mosquitoes do not bite (they don’t blood feed at all) and they’re commonly found in the same type of habitats as the mosquitoes that transmit dengue (e.g. Aedes aegypti). While some positive results may be observed where the immature stages of Toxorhynchites are present, the factors that drive predator-prey relationships are a likely barrier to long term success. Predators need prey and there is often a delay between the build-up of prey populations before predators respond and, with regard to mosquito-borne disease management, that is a relatively ineffective strategy.
5. Mosquitoes provide food for bats. There are some phenomenal claims floating about regarding the quantity of mosquitoes insectivorous bats can consume each night. These bats certainly eat mosquitoes but recent studies have shown that they’re not their favourite food. There is no evidence that they significantly reduce local mosquito populations. Studies investigating the ecological importance of saltmarsh mosquitoes in coastal regions of Australia revealed that insectivorous bats shifted their foraging behaviour in response to changes in local mosquito populations but when molecular analysis was conducted on bat poo to identify mosquito and moth DNA, it showed that only about half of the smallest bats collected were eating mosquitoes while all the bats studied were eating moths. This probably means mozzies are more snack food that a stable when it comes to the diet of bats…but who doesn’t some junk food every now and again?
6. Mosquitoes clean up ant vomit. If you thought the idea of feeding on blood was a little icky, how about feeding on substances regurgitated from ants? There is an unusual group of mosquitoes that belong to the genus Malaya that are specialists in making a meal of ant vomit. The mosquito is active during the day, rather than the evening, and seeks out ants (typically those of the genus Crematogaster) on tree trunks. The mosquito has a modified proboscis so that when it confronts an ant, it brings the tip of its bulbous proboscis into contract with the mouth of the ant, forcing open the ant’s jaws until a drop of liquid is produced. The mosquito quickly slurps up the regurgitated liquid and the ant is left to go on its merry way unharmed. Cool huh?
7. Mosquitoes sing sexy songs. Ever serenaded a potential love interest? Male and female Yellow Fever Mosquitoes, Aedes aegypti, “sing” to each other in a duet of wing beat frequencies. It is a phenomenon known as “harmonic convergence” whereby the mosquitoes hit the high notes of 1200 Hz together; a harmonic of the fundamental frequency of both the female (about 400Hz) and male (about 600HZ). Something to think about next time a mosquito’s buzz is keeping you awake!
8. Mosquitoes pitch in to help pollinate plants. As blood feeding is primarily required for egg development, both male and female mosquitoes require an energy hit from sugars for other day-to-day activities. Does this mean that mosquitoes may be important pollinators of plants? A study of the blunt-leaved orchid, Habenaria obtusata, found that mosquitoes may be important pollinators with species, Aedes communis and Aedes canadensis canadensis most likely the key pollinators. However, subsequent studies identified moths, as well as mosquitoes, as potentially important pollinators. What these studies seem to indicate is that while mosquitoes are able to take advantage of a newly opened flowers full of nectar, moths have the advantage of possessing a longer proboscis and enables them to successfully feed on a greater proportion of flowers. It seems that when it comes to pollination, size does matter.
9. Mosquitoes have worked out how to deal with hot drinks. Ever felt nervous grabbing that take away coffee? How about mosquitoes that are typically at the mercy of changing environmental temperatures, what happens when they take a blood meal that may be twice as hot as the ambient air temperature? A recent study showed that taking a blood meal can rapidly increase the temperature of a mosquito by 10C and that in response, the mosquito produces heat shock protein that help with blood meal digestion and egg production. These heat shock proteins have been found in a number of other mosquitoes and blood feeding insects but for the mosquitoes that spread malaria, and even more ingenious method has evolved, bum-based thermoregulation! Researchers have used infrared cameras to study temperature changes in the malaria vector Anopheles stephensi during blood feeding. What the footage revealed was that the mosquito deals with the increased temperatures of blood feeding by excreting and holding a droplet of fluid at its abdomen that allows evaporative cooling of the mosquito to take place.
10. Mosquitoes look awesome. You could be forgiven for thinking that mosquitoes are drab. While beauty is in the eye of the beholder, mosquitoes rarely get a look in when it comes to “best looking insect” competitions. However, there is an amazing diversity of colours and patterns amongst many mosquitoes. From the bright orange of Coquillettidia xanthogaster to the metallic appearance of Toxorhynchites spp., mosquitoes can look as awesome as any other insect. One of my personal favourites is the “feathered” mosquito, Sabethes cyaneus. The distinctive feathery “paddles” on this species is unlike anything else in the mosquito world. They look great but they’ve also been investigated to determine what role they may have in the biology of this mosquito. Although male mosquitoes of this species are known to engage in elaborate courtship “dances”, a study has demonstrated that the presence of the “paddles” on female mosquitoes assist in attracting males. Why do males have the “paddles”? No one is quite sure.