According to the Lepidopterists' Society, the average lifespan of an adult moth varies by species. For instance, sphinx moths typically live two to three months, silkworm moths survive only about one week after emerging from their cocoons and yucca moths die within two days.
The Lepidopterists' Society indicates that short-lived moths have brief lives because they have no way to ingest food. They live on stored nutrients. Their entire function as adults is to mate to produce the next generation of moths.
The amount of time moths spend in the earlier stages of their life cycles -- eggs, larvae and pupae -- varies as well. It depends upon climate, habitat and weather conditions, the Lepidopterists' Society states.