Clover Hayworm Moth

The clover hayworm moth (Hypsopygia costalis) is a pyralid moth in the family Pyralidae, subfamily Hypsopygia, order Lepidoptera. The common name hayworm moth reflects the larval habit of feeding on dry plant material, including stored hay, dried plant debris, leaf litter, and decaying organic matter — a diet unusual among moths, most of which feed on living plant tissue. Larvae of H. costalis inhabit accumulated plant detritus such as thatch, stored grass clippings, compost, and dry stacks of hay or straw, earning the species its association with agricultural storage environments. Adults are small, brightly colored moths with distinctive red, yellow, and ochre wing markings that make them more visible than many pyralids, potentially functioning as aposematic coloration or mimicry. The species is distributed across Europe, including France, Germany, and the United Kingdom, extending to North America. It inhabits a variety of habitats wherever decaying plant material accumulates, including agricultural settings, gardens, woodland edges, and semi-natural grasslands. H. costalis is classified as Least Concern on the IUCN Red List, with populations considered stable and the species not subject to significant threats. The species has one generation per year in most of its range, with adults flying from late spring through summer. Larvae overwinter in plant debris. H. costalis rarely causes significant economic damage despite its association with stored plant material.