Before we begin our delightful discourse on invasion versus infestation, let’;s meet our cast:

• German cockroaches (Blattella germanica) are ¾ inch long and pale brown or tan. They are most prevalent in American homes and businesses. They usually live near food and are difficult to exterminate. They also reproduce exponentially. In several generations one fertile female can produce 30,000 descendants a year. Like Nazis, they are invaders.

• Brownbanded cockroaches (Supella longipala) are ½ inch long and dark brown. These fecund insects prefer warmer environments and can thrive on the protein found in casein glue. One brown supermarket bag can feed several families. They also invade and stay unseen.

• American cockroaches (Periplaneta americana) are 2 or more inches long and pale brown or yellowish. They crave a warmer, humid home and prefer sewers to houses, although if there is construction in a residential area, they have been known to invade nearby homes and businesses.

• Oriental cockroaches (Blatta orientalis) are 1 to 1½ inches long (or longer), and are a dark reddish brown. They are often called “water bugs.” Like their American cousins, they do not generally live indoors, although they can crawl inside a house through an opening the thickness of a penny. Their presence is more properly called an “invasion” rather than an “infestation.” Small comfort.

Sadly, cockroaches do not feed on each other so it is entirely possible that two or more species can coexist in a single environment. Although they are unsightly and offensive, they are not poisonous. But they do tend to dwell in filth, which makes them, their egg pods, and their droppings dangerous to humans and pets. Pest experts advise that, while spray insecticides can provide initial control of roach populations, the more effective control is through spraying boric acid and similar powders.