Experts believe that the earliest insects first emerged on earth nearly half a billion years ago, which is around the time when the first plants emerged. The vast majority of modern insect species undergo either complete or incomplete metamorphosis. Metamorphosis is the multi-stage maturation process that takes place during an insect’s life-cycle. Around 10 percent of all documented insect species worldwide undergo incomplete metamorphosis in which newly hatched nymphs closely resemble adults, but are smaller in size, and consume different foods. Most modern insect species undergo complete metamorphosis in which larvae and adults appear markedly different and rely on different food sources.
Incomplete metamorphosis consists of three stages–egg, nymph and adult, but nymphs pass through multiple stages (instars) of growth in between the shedding of their exoskeletons. Complete metamorphosis is the least primitive form of insect maturation, and it consists of four stages–egg, larvae, pupae and adult. Most of today’s insect species undergo complete metamorphosis, but the earliest insects to emerge were “ametabolistic,” which means that they did not undergo metamorphosis of any kind. These first insect species hatched from eggs as miniature adults, and modern examples of ametabolistic insects include silverfish and firebrats. The next most primitive form of insect maturation is known as “paurometabolous metamorphosis,” and it consists of egg, nymph and adult stages, but nymphs and adults are very similar in appearance and they each inhabit the same conditions where they compete for the same resources.
Ametabolistic and paurometabolistic insects predate winged insects, insects that rely largely on smell to locate food, and insects that possess advanced olfactory organs that are designed for sophisticated pheromone and chemical communication systems. Although cockroaches possess wings and emit and detect pheromones that facilitate subsocial behaviors, their wings are underdeveloped and rarely used, and they possess biologically simple olfactory organs that are insufficient for long distance pheromone detection.
Cockroach pheromones emanate from gut bacteria in their feces, and not from specialized cells in their tissue like more advanced insects. Also, successful pheromone transmission between roaches is largely dependent on physical contact that occurs during grooming, mutual antennae contact and other social activities. Because of this, pest traps and baits that lure insects with synthesized pheromones and food odors fail to attract cockroaches. In order to be effective, odorous traps and bait stations must be placed on the indoor foraging pathways that cockroaches repeatedly take within homes. However, researchers recently discovered sex pheromones and specialized pheromone receptors in female cockroaches, and are currently attempting to synthesize cockroach aggregation pheromones that may attract roaches to bait stations that are located away from their foraging roots.
Have you ever used odor or pheromone traps or baits to control cockroach pests in your home?