To most, a food chain suggests a chain of supermarkets, but another type of chain occurs when the arctic shrimp feeds upon the plankton, the seal on the shrimp, and the polar bear upon the seal.
Biology has long taught that insect design and coloration has purposeful protective value, blending the creature to his environment, or giving an unpalatable appearance. Now, to the contrary, it is suggested that insects as one of the links in a food chain obtain their protection not from startling color schemes, like that of the monarch butterfly, but from feeding upon plants whose juices are poisonous to birds who would otherwise eat the insects. The normal diet of the larva of the monarch is the milkweed, which contains digitoxin glucosides, poisonous to the birds which might otherwise enjoy a diet of these butterflies.
To explore this phenomenon, a group of Amherst biologists trained monarch larvae
THE FOOD CHAIN AND THE MONARCH BUTTERFLY. JAMA. 1967;200(13):1176. doi:10.1001/jama.1967.03120260072013