Five scary animals that help us

(Photo: Geanixx / Wikimedia)

The thought of seeing a shark or a python in the wild is enough to send chills up most people's spines. But some of the animals we're most afraid of are actually good for us.

Some help control insect populations naturally and reduce the need for toxic chemicals. Others are being studied by medical researchers and may be valuable in treating human disease.

Here are some examples of villains that are actually heroes:

Bats have a reputation for being dirty disease carriers (although in China they're a symbol of happiness and good luck). In reality bats do a lot more good than harm. The flying mammals feast on moths, beetles, gnats, crickets, and more so they keep insect populations under control. Some species pollinate flowers and scatter the seeds of plants. Their guano is used as a rich natural fertilizer, a welcome alternative to synthetic versions.

Spiders may be creepy, but most of them are harmless to humans. Tarantulas and other large hairy spiders are particularly scary, but their bite is usually less harmful than a bee sting (unless a person is severely allergic). Spiders reduce the number of mosquitoes and other disease carrying insects. Spider venom and silk may have numerous medical benefits in the future. Scientists are studying how it can help treat arthritis, neurological disease, impotence, and more.

Ball pythons, or any pythons for that matter, are not poisonous. Instead they kill by constricting their prey, typically small rodents such as mice and rats. They prevent overpopulation of rodents and its harmful affects on the environment.

Sharks do kill a few people each year, but unprovoked attacks are rare. At the top of the ocean food chain, sharks play a valuable role in maintaining the ocean's ecosystem. As the number of sharks decrease, the number of small fish we don't like to eat grows. Medical researchers are studying sharks' amazing immune systems and hope to shed light on curing human disease.

Vultures eat animal carcasses. Believe it or not this is a huge public service. By removing dead animals that can harbor bacteria and disease, the scavenger birds keep the environment clean and prevent disease from spreading.

Check out Yahoo! Green on Twitter and Facebook.