It seems that almost everywhere I go on an outdoor excursion (especially when hunting for waterfalls), mosquitoes are around. It doesn't matter whether I'm in the alpine meadows and forests of California's Sierras, the moors of Northern Norway, the tropical jungles of the Pacific Islands, the billabongs of Northern Australia, or even the desert oases of Southern Utah. It seems that mosquitoes are everywhere looking to draw my blood. And the itchy welts they leave afterwards can be quite annoying.
So why are they everywhere? Is there any cause for concern about them? What can be done to cope with them? To answer these questions, I did a little research and found out that in Nature's system of checks and balances there are things we ought to know about these pesky little buggers.
There are many reasons why mosquitoes are so widespread around the planet. Like almost all organisms, they rely on water to survive, but in this case, they tend to favor standing pools of water to lay eggs. Standing pools of water can be found at some moments during the year in nearly all climate zones except the arctic cold of the polar regions (though Global Warming is changing this). For example, melting snow in the alpine regions can saturate the ground in late spring and early summer to create marshy conditions full of standing water in meadows, valleys, and plateaus. This also explains why mosquitoes are found in the desert lining rivers, creeks, and springs as water is scarce and only concentrated in these areas on the surface. Moreover, the tropical regions are natural places to harbor standing pools of water as the humidity, frequent rainfall, and dense vegetation help maintain the conditions favorable to mosquitoes throughout the year. In fact, the tropical regions are where the species are most abundant, and unlike other climate zones, they do not have population variations where their numbers significantly reduce or grow depending on the seasons. So given all these factors, it's no wonder why I constantly run into mosquitoes in my waterfall adventures as we standing water is an inevitable part of such ecosystems.
Fossil records have shown that mosquitoes have survived for over 30 million years, and related ancestral species have dated back to over 100 million years. This means that they have not only used this time to successfully spread their population throughout the world, but that they have evolved to become very good at what passing on their genes to their offspring to prolong their existence as a species. It's surprising to note that for the most part, it's only the female mosquitoes that bite. That's because they need the proteins from the blood of birds and mammals (including humans) to properly nourish their eggs, which are laid in mostly standing water habitats. Their sensor-like design is perfectly adapted to detect chemicals, motion, and heat. For example, they can detect carbon dioxide and lactic acid emissions from our breathing and our sweat, they can sense when something contrasting with the background moves, and they can tell if something is giving off heat (especially from warm-blooded organisms). Take all of these factors into account and it's no wonder why mosquitoes never seem to leave you alone as well as hone in on you like a heat-seeking missile.
The mechanism by which mosquitoes draw blood is through a multi-syringe-like mouth called the proboscis. It is through the proboscis that saliva (containing anticoagulants) is secreted to keep the blood from clotting and thus making it easier for the mosquito to draw blood - often times without you feeling anything due to an anesthetic-like substance. However, it's also this saliva that tends to induce an allergic reaction that often swells and becomes itchy. That's usually when we finally realize that we've been bitten. Usually their bites are merely annoyances, but mosquitoes can also pick up viruses and bacteria from one organism and transmit them to others - thus making them disease vectors. It is this fact alone that has perhaps made mosquitoes one of the biggest killers (at least to humans) on the planet. It has been said that more people have died from mosquito-borne illnesses such as Yellow Fever, Malaria, Encephalitis (including West Nile), Dengue Fever, etc. than has all the wars throughout human history combined! Mosquito-born diseases are transmitted to 69 million people with 5.3 million of them dying every year. This explains why certain regions of the world seem to be very prone to such diseases (e.g. the presence of malaria in Malaysia). With the advent of Global Warming, the population of mosquitoes and the consequent spread of diseases will increase as more parts of the planet will have climates favorable to their existence.
There are some measures we can take in order to prevent or minimize the adverse impacts of mosquitoes on us while participating in nature-based activities. One approach is to wear enough clothing to minimize the amount of exposed skin. The problem with this is that mosquitoes are usually located in warm and humid areas so this can make you unbearably hot while losing more water through sweat to keep the body cool. A second approach is to apply bug repellant containing DEET, which seems to be quite effective in confusing the mosquitoes' chemical sensors. Unfortunately, there are certain health risks associated with this chemical (it has been known to burn plastic) so it ultimately comes down to a trade-off between your assessment of the risk of disease versus the unintended effects of DEET. There are other types of repellant out there, but they don't seem as effective (e.g. in my experience, Avon's Skin So Soft hardly works even though it's not as toxic as DEET-based repellants). Finally, you can do the best you can to keep moving since mosquitoes can only fly so fast and for so long. Usually a combination of the above measures gives you the least chance getting bit by a mosquito while being out in nature because each of these measures has drawbacks.
In conclusion, the relationship between mosquitoes and humans are all part of the checks and balances of Nature and natural selection. In other words, we are part of the food chain and the cycle of life. And it is for this reason that they play a key role in supplying food for other insects and more complex organisms feeding on them. So we ought to respect the mosquitoes as survivors as well as role players in the overall scheme of things. Even though most of us don't like them, they're here to stay so we mind as well cope with living with them.