Flutterby

Flutterbies are a sapient species which, in their immature state, resemble giant caterpillars.

Biology
Flutterbies are carbon-based lifeforms which evolved on a terrestrial planet orbiting a G-type star. They are herbivorous, but flexible in their diets. They're also a dioecious species, meaning that individuals will be either male or female, much like Humans.

Larval stage
In their immature stage, their bodies are long and segmented, with multiple pairs of short legs for locomotion. They have mobile eyestalks and three jaws. They weight about half as much as an adult Human being and require similar environmental conditions to Humans, although they don't seem to be bothered by Siberian tundra temperatures and remain unclothed. They are, however, considerably vulnerable to the ultraviolet light emitted by the Earth's sun. This immature stage is fully intelligent and can live for several decades, postponing their maturity by chemical means.

Imago
When a Flutterby reaches maturity, a drastic metamorphosis takes place and they lose all of their sapience and reasoning capacity. They gain wings, lose all of their digestive system and most of their neural system and become little more than mindless breeders, which can live for ten or eleven days at most. Younger siblings and nieces take care of them and protect them while they're going through the chrysalis stage, and help raise the offspring later on.

Culture and society
Flutterbies are described as gregarious creatures, and seem to enjoy the company of strangers. Their civilization can probably be considered a Type I in the Kardashev scale, as they are known to master interplanetary industry, but don't seem to have evolved interstellar flight yet. Instead, they will travel to other star systems as passengers in the Chirpsithra interstellar liners.

Flutterby society seems to have a rigid caste system, divided between "citizens" and "servants", with the servants being referred to with the same pronoun they use for machinery. Individual Flutterbies aren't usually allowed to speak to those of a different caste than them, except in the context of giving and receiving orders.

Immature Flutterbies can often be found living in mating groups of six or seven individuals (husbands and wives). The group decides collectively when it is time for them to go into chrysalis. After emerging from the chrysalis, the Flutterby's life is destined to end soon; all they do is mate and die within a few days.

Appearances

 * "Chrysalis", by Larry Niven (2002)
 * "The Death Addict", by Larry Niven (2003)