Repellency
A foul smell or a bad taste is often enough to discourage a potential predator. Shield bugs (often called stink bugs; order Hemiptera), for example, have specialized glands located in the thorax or abdomen that produce foul-smelling hydrocarbons. These chemicals accumulate in a small reservoir adjacent to the gland and are released onto the body surface only as needed. The larvae of certain swallowtail butterflies (order Lepidoptera, family Papilionidae) have eversible glands, called osmeteria, located just behind the head. When a caterpillar is disturbed, it rears up, everts the osmeteria to release a repellent vapour, and waves its body back and forth to ward off intruders. Similar eversible osmeteria, but located on each side of the thorax and abdomen, are found in adult beetles (Coleoptera) belonging to the family Malachidae. The larvae of some leaf beetles (order Coleoptera, family Chrysomelidae) cover themselves with their own slimy, black excreta - no doubt distasteful and certainly not an appetizing sight!"
http://www.kendalluk.com/defence.htm
The other can be found at 44-45 s at
http://www.youtube.com/watch?v=yuY44PHC0…