Warm summer weather means more insects — along with more people trying to enjoy the outdoors while avoiding pesky pests. However, some are more than a mere nuisance. Although bugs are a crucial part of the ecosystem, some small creepy crawlers pose big threats to humans and animals.

When you think of deathly, dangerous bugs, it's a good bet you think of some myth-like monster in some far-flung locale. You know, the Tse Tse fly in Tanzania, or the wandering spider in Brazil. It might feel like the United States is an insect-free oasis—at least compared to Australia, where spiders literally fall like raindrops, by the thousands, in a terrifying phenomenon aptly dubbed, "spider rain." But the unfortunate reality is that dangerous insects are likely lurking in your own backyard.

In the case of Hawley Crippen, the unusual poison choice, Hyoscine, led investigators to question the validity of the remains. It seemed unusual for the toxicologist to check immediately for the common alkaloids before looking for more common poisons. But what are the more common poisons used in murders?

As far as the murder of individuals is concerned there are relatively few agents that have been used and of course there is no way of knowing how many people have been deliberately killed this way because no doubt many such deaths were attributed to natural causes.