Ever since my friend's husband got really, really sick with what the doctor said could either have been spinal meningitis or West Nile Virus, I have been really paranoid about mosquito bites. I have them all over my legs and toes because I am also, unfortunately, paranoid about putting chemicals, including insect repellent, on my body. It is hard to say in some cases which is more dangerous, the disease or the cure. However, in the case of mosquito bites, I think the diseases are pretty frightening.
I have done some reading about mosquitoes recently in a book called Field Notes from the Northern Forest by Curt Stager in which he pretty thoroughly explains the predicament of biting bugs in a chapter aptly titled, "Why Do Bugs Bite?". He explains that it is only female mosquitoes who bite. Male mosquitoes, who bunch together in clouds at dusk to attract females, don't bite at all. In fact, most of the time, most mosquitoes feed only on sugar water from plants. However, after insemination,
"[the female mosquito's] reproductive tract is freshly loaded with sperm, and hundreds of fertilized eggs are growing inside her abdomen. Each egg is a living, growing cluster of cells draining her maternal tissues of protein and minerals. She must replace those losses or die, and mere sugar water is not rich enough in the necessary compounds. Only blood will do. This is why biting flies bite, and why it is only the females that do so... It is hard to feel sympathetic about the lot of a female mosquito. But think about it: She is risking her life by approaching you, and she only does so for the sake of her unborn young, albeit instinctively. The risk is more than just a chance of being swatted. From her perspective, we humans are the ones who carry the parasites... If you happen to be suffering from filariasis, a single blood meal from you can send a swarm of nematodes down her throat. Once inside her gut, the worms bite their way out of her stomach and burrow into the fibers of her flight muscles..."
He further explains that there are many species of mosquitoes that don't bite humans at all. It is unfortunate that they are so tiny we can't tell apart the ones that bite from the ones that don't, but in any case, it's a good idea to make sure there is no standing water near your house, since that is where they breed. It is pretty fascinating to think of things from a bug's point of view, but it is hard to feel sorry for an insect that's been around for 170 million years and spreads disease to 700 million people a year. So maybe they don't *mean* to spread disease, but they are a serious threat to human life, particularly in regions of the world plagued by malaria.