Pat Barker's novel Regeneration (1991) centres on the pioneering methods of the British psychiatrist W. H. R. Rivers, who treated a number of shell-shocked soldiers – including Wilfred Owen and Siegfried Sassoon – during the First World War. After meeting with a severely traumatised young veteran who is beginning to show signs of a ‘complete disintegration of personality’, Rivers recognises something hopeful in his patient's declining mental state:

The pupal stage of insect life is here called upon to express a curious psychic phenomenon, in which the mind of the shell-shocked subject appears to degenerate further during the initial stages of recovery. As the passage indicates, there are long-standing associations between the ‘human soul’ and lepidopteron life forms: Aristotle first attested that the word psyche, meaning soul, mind or spirit, is also Greek for butterfly or moth. The physicality of Barker's ‘rotting’ chrysalis, however, with its suggestion of knowledge gained through observation (‘Cut a chrysalis open and you will find …’), is perhaps more in keeping with Rivers's frequent recourse to entomology in his writing. In her cultural history of myrmecology, Charlotte Sleigh identifies ‘numerous references’ to studies of insect life in Rivers's published works, arguing that ‘for him … Insecta were illustrative of the deeper recesses of the human psyche’.

Published in 1920, Rivers's study Instinct and the Unconscious: A Contribution to a Biological Theory of the Psycho-Neuroses outlines a theory of nervous disorder that results from the disruptive resurfacing of primordial instincts, such as immobility, aggression and nervous collapse, in response to danger. Building on the findings of Fabre and others, Rivers likens this phenomenon to the way that certain butterflies preserve responses to stimuli that were aroused during the caterpillar stage.