Cockroaches

Updated September 26, 2026 · The Pest Guide · Editorial policy

When you flick on the kitchen light late at night and watch a flattened, fast-moving insect with sweeping antennae scramble for the nearest crack under the dishwasher, you are looking at a cockroach. What ties these creatures into a single recognizable group is a remarkably practical body plan featuring a broad, shield-like head cover that hides their face from above, six spiny running legs built for horizontal speed, and leathery wings that overlap flat at rest. People often confuse them with ground beetles or crickets, but beetles sport hard shell-wings meeting in a straight center seam with their heads fully visible, while crickets have oversized hind legs built for hopping, neither of which any cockroach can do.

Inside this single biological catalog, you find a sharp split between true domestic indoor reproducers, like the tiny German cockroach that thrives near kitchen grease, and peridomestic outdoor wanderers, like the Pennsylvania wood roach that simply wandered in from the firewood pile looking for moisture. Domestic species pose serious public health concerns by carrying food poisoning bacteria and shedding potent allergens that trigger asthma, whereas outdoor invaders usually die quickly indoors because they belong outside in leaf litter and mulch. Sorting out which kind you have matters because an indoor infestation requires rigorous sanitation and exclusion, while a stray outdoor visitor just needs a door sweep and a moment of perspective.