Although only a few of the 3,500 species of cockroaches infest houses, they have earned notoriety for the entire order. Because its taste in food is so wide-ranging, the common cockroach can scavenge in any environment. Within man's shelter alone it can derive nourishment from such diverse materials as wallpaper, food scraps, other household insects, stale beer, watercolors, and white-wash. Attempts to exterminate them invariably prove futile, for these hardy insects have survived all enemies for at least 230 million years.

   The earliest fossil cockroaches date from the Carboniferous period. In fact, so prevalent are the Blattaria in these deposits that one scientist has nicknamed it "the era of the cockroach." Structurally, these early forms were remarkably similar to present day in­sects. Because they were already exception-ally well developed and had already separated into a large number of distinct species, entomologists believe that they must have been among the first insects on earth. They were, in any case, the first capable of flight.

   Today, most cockroaches are found in regions where the average temperature is above 77° F. and the relative humidity greater than 50 per cent. This usually means a tropical habitat. Tests have shown that cockroaches can withstand temperatures as high as 120° F. but die at temperatures be-low 20° F. In colder areas they naturally gravitate toward human habitations, where temperature and humidity are kept comfortable even in winter, and where food of some sort is always abundant. The migration of the three indoor species most com­mon in the North — Blatta orientalis, Periplaneta americana, and Blattella germanica — has ironically been aided most by man himself. Cargo ships from the tropics have been plagued by cockroaches for centuries. Indeed, records show that seventeenth-century English vessels were infested with these insects from crew quarters to food stores, and ships' captains tried various, ultimately futile, methods to exterminate them.