Caterpillars of moths in the family Limacodidae produce pain-inducing defensive venoms that have evolved independently to previously characterised lepidopteran venoms, but their composition and mechanism of action are unknown. Here, we examine the limacodid venom system using the species Doratifera vulnerans as a model. Large secretory cells at the base of each spine produce a complex venom (151 proteinaceous toxins in 59 families) that consists predominantly of peptides <10 kDa. Three abundant families of venom peptides (vulnericins) are analogues of adipokinetic hormone/corazonin-like neurohormone that activate the endogenous receptor with picomolar efficacy (Family 1); cationic peptides related to cecropin that disrupt lipid bilayers, induce pain, and kill bacteria and helminths (Family 2); and disulfide-rich knottins (Family 3). Our data reveal convergent molecular evolution between limacodids, hymenopterans, and arachnids, and highlight the potential of Limacodidae for peptide biodiscovery.