The allergens left behind by cockroaches are often very irritating to humans and have been known to cause sickness, allergies, diarrhea, and even child asthma. A cockroach can survive for more than a month without food or water and over 45 minutes without air.
It is often said, "For every one cockroach you see, there are 1,000 more in the walls." This is unfortunately more true than not as cockroaches reproduce very quickly and prefer dark, secluded areas like behind stoves and in the walls. Cockroaches will eat almost anything, but prefer greasy, sweet foods left behind in the kitchen. When one cockroach discovers food, it releases a chemical into its feces which will guide other roaches to the find.
Most roaches are oviparous - their young grow in eggs outside of the mother's body. In these species, the mother roach carries her eggs around in a sac called an oothecal, which is attached to her abdomen. The number of eggs in each oothecal varies from species to species. Many female roaches drop or hide their oothecal shortly before the eggs are ready to hatch. Others continue to carry the hatching eggs and care for their young after they are born. But regardless of how long the mother and her eggs stay together, the oothecal has to stay moist in order for the eggs to develop. Newly hatched roaches, known as nymphs, are usually white. Shortly after birth, they turn brown, and their exoskeletons harden. They begin to resemble small, wingless adult roaches. Nymphs molt several times as they become adults. The period between each molt is known as an instar. Each instar is progressively more like an adult cockroach. In some species, this process takes only a few weeks. In others, like the oriental cockroach, it takes between one and two years. The overall life span of cockroaches differs as well - some live only a few months while others live for more than two years.