Thousands of species of fleas have been identified worldwide, but the fleas that people most often encounter tend to be in the family Pulicidae. They may have names like dog flea, cat flea, and human flea, but most don’t care about the taxonomy of their host as long as it’s warm-blooded.
Fleas are very small and are laterally flattened. A flea’s life cycle is also brilliantly fine-tuned for survival. Flea larvae are tiny, blind, legless, wormlike scavengers that develop in dark, humid places like cracks on the floor, animal nests, bedding, etc. There they eat organic matter including dead insects, dandruff, exfoliated skin, shed insect skins, plant material, and flea feces. After a week or two as larvae, they spin silken pupal cases. Fleas spend a week or two as pupae. They may hatch immediately, or they may remain dormant in their pupal cases until they sense the approach of a host