Hydraecia micacea

Reliable identification from similar European Hydraecia species (H. ultima and H. nordstroemi) requires genital examination; external morphology is insufficient for definitive determination. Within its range, distinguished from H. immanis (hop-vine borer) by specific morphological and molecular characteristics. The rufous-tinged forewings and luteous hindwings provide tentative field recognition, but confirmation necessitates dissection.

Forewings variable in ground color from pale greyish-ochreous to dark grey or brownish-grey with strong rufous tinge; median area darker, suffused with olive brownish except along costa and inner margin; inner and outer lines brown; upper stigmata large with fine brown outline; submarginal line variable, sharply angled on vein 7; hindwing luteous, generally grey-tinged with dark outer line and submarginal cloud. Wingspan 28–45 mm; forewing length 14–21 mm. Larva reddish flesh color with deeper dorsal line, yellowish sides with black-dotted lateral line above feet, black tubercles and spiracles, yellowish thoracic and anal plates, shining red-brown head.

Agricultural and semi-natural habitats including hop gardens, potato fields, and areas with herbaceous vegetation; larvae occupy subterranean environments within host plant root systems and crowns.

Native across the Palearctic realm from Ireland to Siberia (excluding southern areas), extending to Japan. Introduced to eastern North America including Quebec, Ontario (Ottawa), and the northeastern United States. Present in Belgium at regional scales.

Adult flight period from early July to November; single generation per year. Egg laying occurs in autumn. Larval activity from spring through summer, with pupation in July–August. Exact timing varies geographically; Belgian and Dutch records indicate July–November flight season.

Larvae feed on roots and crowns of herbaceous plants including Humulus lupulus (hop), Solanum tuberosum (potato), and a wide variety of other herbaceous species; feeding is subterranean.

• Humulus lupulus - larval hostroots and crowns; significant agricultural pest in hop cultivation
• Solanum tuberosum - larval hoststems and roots; females call from concealed positions within potato stems

Univoltine. Eggs laid on host plant stems in autumn, overwintering until hatching in early May. Larvae initially tunnel in host bines (April–June), then feed subterraneously on roots and crowns through spring and summer. Pupation occurs in soil near damaged plants during July–August. Adults emerge late summer to autumn. Complete cycle spans approximately one year.

Females exhibit calling behavior beginning on the first night after emergence, with peak activity 2–4 hours into scotophase; calling duration increases with age, reaching maximum on night 3. Females call from concealed positions within host stems rather than exposed locations. Males are attracted to calling females. Larvae exhibit subterranean feeding habit, tunneling into root tissues and crowns. Nocturnal adult activity typical of Noctuidae.

Agricultural pest causing significant economic damage to hop and potato cultivation through destruction of root systems and crowns; larval tunneling may predispose host plants to secondary infection by Fusarium canker.

Significant agricultural pest of hops and potatoes; economic losses documented in European hop gardens and North American potato fields. Chemical control with DDT historically effective; modern integrated pest management approaches developed. Genome sequenced for research purposes (Wellcome Sanger Institute, 2023).

• Hydraecia ultimaOverlapping distribution in Europe; external morphology very similar; requires genital examination for reliable separation
• Hydraecia nordstroemiOverlapping distribution in Europe; external morphology very similar; requires genital examination for reliable separation
• Hydraecia immanisSympatric in North America; historically confused with H. micacea; distinguished by morphological and molecular characteristics

• agricultural pest
• univoltine
• subterranean larva
• Palearctic native
• introduced species
• genome sequenced

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Biology, Damage and Control of Rosy Rnstic Moth, Hydraecia micacea (Esp.), on Hops
• Calling Behavior of the Potato Stem Borer, Hydraecia micacea Esper (Lepidoptera: Noctuidae), in the Laboratory and the Field
• Biology and Phenology of the Hop-vine Borer, Hydraecia immanis Guenée, and Detection of the Potato Stem Borer, H. micacea (Esper) (Lepidoptera: Noctuidae), in Wisconsin
• The genome sequence of the rosy rustic, Hydraecia micacea (Esper, 1789).