A droll and clever appreciation of inquilines. Inquilines? Animals that move into the homes of other animals. Or, as McLoughlin has it, the ones that, defying traps and poisons, ""continue to participate in our lives-with enthusiasm."" One thinks first of creepy-crawlies, the ones we must stoop to conquer, but this breezy biologist saves the best for last and begins with larger specimens. Like house sparrows, actually weaver birds, whose U.S. immigration can be traced to a few misguided Brooklynites and whose deep ancestral roots permit the author an engaging detour through the Neolithic because ""House sparrows. . . are dinosaurs."" Or starlings: omnivorous, aggressive, with a miraculous digestive system, complex language, fine hearing and cognitive powers. Also, they taste good--a likelier solution to starling overpopulation than all those failed extermination schemes. Pigeons enjoy a unique protected niche in the human community; kept alive by dedicated bread-crumb strewers, they steadily augment air pollution and carry a load of foul diseases. Plus mice--extraordinarily fecund, possessors of efficient kidneys, somewhat redeemed by their laboratory contributions; and those ""exuberantly successful"" rats--peerless food supply contaminators, whose sensitive whiskers enable movement in the dark. Good enough, but when McLoughlin reaches the arthropods he soars. ""Nowhere else but among the arthropods is evolution so careless of the individual, so thoughtful of the type."" And so we see silverfish who thrive on bookbinding glue, plucky roaches, beetles (""representative of life at its ebullient best""), houseflies, ants, scorpions (""beautiful in their glistening armor""), and spiders. Don't expect Lewis Thomas: there are stops for schoolboy irreverence, along this house tour. But McLoughlin is a cheery guide, agile and well-armed, and he's illustrated this odd lot with very stylish precisionist black-and-white drawings.