In the world of Wyndham's novel The Chrysalids, the "chrysalids" themselves are the children strewn all over the world who have a particular ability, regarded as a "blasphemy" in their post-apocalyptic and backwards culture. The children are telepathic, or able to communicate with each other over long distances. The group of telepathic children are supported by some sympathetic adults, but for the most part, "blasphemies" are forced to flee to the Fringes, as the mainstream people believe blasphemies will cause another "tribulation" or apocalypse.
As described in the previous answer, the word "chrysalid" is itself a variation on Latin chrysalides, and to the modern mind it first evokes the state in which a pupa finds itself while it is transforming into a butterfly or moth. If being in a chrysalis is, then, a state of transition or evolution, the Chrysalids in this story represent the changing state of the world depicted. They are also, more literally, in a state of evolution themselves, as, at the beginning of the novel, the telepaths are all struggling to fit into a world that rejects them, by keeping their abilities hidden. Meanwhile, by the end of the story they have gained the strength and increased telepathic power to reach out and find each other and the more advanced people on the other side of the world, in Sealand. The story, then, is the process of their own individual chrysalis or metamorphosis.