Pheromones are the primary mechanism for communication among insects. The word is derived from Greek, pherein, to carry and horman, to excite. Although released and detected in minute amounts, pheromones have profound biological effects in receptive organisms. The main function is triggering sexual attraction and stimulation, but some forms can signal danger or lead members of both sexes to food. Pheromones are usually chemically simple compounds such as esters, alcohols, epoxides, aldehydes, ketones, ethers or even hydrocarbons. Two examples are muscalure and bombykol, the sex attractants of the housefly and silkworm moth, respectively. They typically have low molecular weight, low enough to be volatile but not so low as to disperse too rapidly. They are also highly specific, logical as species survival would not be helped with a molecule attracting members of the wrong species. Often this specificity is achieved through stereoisomerism, but some species use specific ratios of multiple pheromones to communicate a particular message. | 
