As someone who spent most of her childhood outside playing in the woods I've encountered many insects. I don't even remember how many times I've been spit, peed,pooped,or sprayed on by little critters. One insect that I am glad I've never picked up is the bombardier beetle Stenaptinus insignis. This insect's chemical spray burns. The chemical's held in its body have to be kept in separate chambers in the beetles abdomen until it feels attacked. The reason for this is that when the two chemicals mix they create an explosion. Essentially a bomb goes off in the beetle's butt. If the loud bang doesn't deter the attacker the beetle has a back up. The chemical not only irritates the skin, but burns it as well. The chemical reaches a temperature of 212 degrees Fahrenheit. The bombardier beetle has almost perfect aim.




Another interesting thing about this beetle is its ability to reach any part of it's own body in order to reach a predator. Its own body is immune to the chemical and it is neither irritated or burned. Scientist are baffled by this and have no clue what about the beetle keeps it safe from its own attack.




http://insects.about.com/od/coolandunusualinsects/a/bombdefenses.htm
http://news.bbc.co.uk/2/hi/science/nature/422599.stm