Roach on ceiling: A common sight in human dwellings, this is a cockroach that has ventured onto the ceiling, possibly seeking food or shelter. Cockroaches are nocturnal insects that are attracted to warm, humid environments. They are omnivorous and feed on a variety of organic matter, including food scraps, pet food, and even human skin. Cockroaches can transmit pathogens and allergens, and their presence can trigger respiratory problems.