Cockroaches are long, flat, brown insects. Their heads point downward and have chewing mouthparts. A plate from the top of the thorax covers the head when you look down on them, so you can't actually see the head. They are very fast runners. They have long antennae, and at the end of the abdomen are two short antennae-like structures that sense air current and vibrations.
There are over 4,000 species of roaches spread all around the globe, and lots more still unknown to science. In Michigan there are only a couple of dozen species, and about half of them are invaders that came along with European settlers.
Most cockroach species live in dead leaves and soil on the ground in forests. A few well-known species have adjusted to living with people in houses and other buildings.
Cockroaches have incomplete metamorphosis. Immature roaches look pretty much like adult roaches, except they don't have wings yet. As they grow the molt (shed their whole skin at once) several times. After the last molt, they roach has wings and can reproduce. It stops growing and molting at that point.
Lifespans vary with species. Some can live for two years.
Most roaches are solitary nocturnal scavengers. Those living in buildings prefer locations that are warm and or damp. A few wild species are more social and live in groups. These species can eat wood (they have special microbes in their guts like termites) and live in decaying logs.
Most roach species use touch and taste/smell as primary senses, but some also communicate with vibrations or other sounds. They hiss, or rub their wings together. The sound startles predators and gives roach a chance to escape, and is sometimes used to attract the opposite sex.
Roaches are scavenging omnivores, they'll eat just about any organic matter they can find. They don't have a powerful bite, so they don't usually eat living animals.
Most roach species don't have any special defenses, they just hide, only come out in the dark, and run fast. A few species have chemical defenses.
In wild habitats, roaches help breakdown dead plants and animal waste.
Cockroaches are the biggest household pest problem in most cities and towns. They spread bacteria that can make people sick.
The great majority of roach species never bother people. They live outside, and are a harmless part of foodwebs.
No roach species are considered endangered.
George Hammond (author), Animal Diversity Web.