The California brown tarantula is brownish-black and can grow to 5 inches long. Although they may look intimidating, a tarantula’s venom can subdue only beetles, grasshoppers, or small spiders — they don’t harm humans. The spiders live underground and are primarily active at night. In the fall, males emerge and wander in search of females. You are most likely to spot them in Rancho Cañada del Oro or Sierra Vista open space preserves. When a male finds a female’s silk-lined burrow, he knocks to announce his arrival. Males die within weeks of mating, but females can live to be 25 or 30 years old.