Alien (Love is the Plan the Plan is Death)

This is an unnamed sapient species with an interesting life cycle. They are notable for their sexual dimorphism, and also peculiar in that their ability to think and learn is directly influenced by the environmental temperature. While their homeworld goes through its warm season they are fully intelligent and telepathic, but the more the cold winter approaches the less they retain the ability to think coherently, and eventually start being driven by pure instincts.

Biology
Members of this species look vaguely like huge insectoids. They have six ambulatory legs at least; several pairs of eyes; a pair of large hunting claws; a pair of more delicate hands which are usually kept hidden; an inflatable throat-sac; spurs; and a tail. Their bodies are covered by armor plates and fur, which is golden-colored in the children, red in the adult females and black in the adult males. They grow in size enormously during their relatively short lifespan, with the full-grown adults being apex predators of their environment. The females care for the young and secrete "juices" to feed them. The males on the other hand produce a substance similar to silk which they weave with their "tender hands", which are usually retracted and hidden.

Life cycle
The children are born in the beginning of the warm season: the one most adequate for thinking and learning. Members of this species lose their ability to learn and to think consciously as the weather gets colder, to the point that they entirely lose their sapience and start acting by instinct alone.

As the cold season begins, the children start to molt, replacing their golden juvenile fur for a red or black one according to gender. At this point the maternal instincts of the Mother start to wear off and she sends them away. Children who remain in the cave might even be killed and eaten by the Mother. After they leave the cave, the young females are picked up and nurtured by matured males, while the younger males spend their first year outside the cave living by their own, learning to hunt and survive.

During the peak of the cold season, these young males eventually give on to their instinct and migrate to the mountains, where they fight (often against their will as they are little more than slaves to their instincts by this point) and kill each other. The survivors retreat to an animal-like existence in the Caves of Winter, feeding on the corpses of those they killed. By the time the weather is warm again and they have regained consciousness, the now mature males emerge to find out that they have grown much larger than their original size.

The mature male typically finds (and falls in love with) a young female, which is at this point a minuscule and bright red creature, smaller even than the smallest eyes of the male. Using his retractable "tender hands" for the first time in life, he weaves the silk produced by his jaws and wraps it around the female's delicate body. From this point on, he carries the female around, nurtures her, feeds her and protects her. After some time the couple starts communicating telepathically, until their minds merge into a single one. When the female has grown too big to be carried easily, the male eventually builds a cave for them to live and spend the next winter.

And then, finally, the cold weather returns. The female has by this point grown to be as large as the male, and her pale pink fur gives way to a fiery red gold-tipped coating. The male no longer covers her in silk. After mating occurs, the female devours the male to provide food for the offspring that are soon to be born, thus propagating the cycle. It is implied that the male's consciousness is transferred to the female, enabling her to learn how to hunt and properly nurture the young ones.

Culture and society
Despite being a sapient species, these creatures have no technology of any kind. They live in burrows they dig in the forests and valleys of their home world. The males hunt to feed both themselves and the females, until the female gives birth to the offspring, at which point she becomes the hunter and feeds the young ones. They have been observed to practice a sort of primitive farming: trapping small animals inside tunnels of silk and providing plants to feed the "livestock".

History
Sadly, it appears that the reign of this species (as an intelligent race at least) is inevitably going to end: the winters are getting longer each year, a fact which at least some individuals are aware of due to the fathers passing the information to the mothers before dying; who then transmit it to the children. With the winters growing longer they keep losing more and more of their thinking abilities and self-control. The very life cycle of the species prevents them from trying to find a solution to the problem, as the adult males are solitary in their first year, and far too concerned with their love lives in their second year; while the females have no learning period and thus are only concerned with their love lives and caring for the children.

Appearances

 * Love is the Plan the Plan is Death, by "James Tiptree Jr.", pseudonym of Alice Sheldon (1973)