73.0885 Spodoptera frugiperda (Fall Armyworm)
ws: 32-40mm (Wikipedia); polyphagous, mainly on grasses and grain crops e.g. corn
Native to North and South America it is a long distance migrant. It was found in Africa in 2013 and is now widespread throughout the continent; it has also been found in India, SE Asia and Australasia. Records are increasing in southern Europe as a result of migration, but it is not yet considered to be established. Moth Dissection shows one undated Irish record but until publication of this St Mary's record it did not have a RES checklist number. The vernacular name "Armyworm" refers to the invasive behaviour of the larva which is a serious pest of several crops - hence the specific name "frugiperda" which means "lost fruit". It a notifiable quarantine pest and has been intercepted at UK customs on >100 occasions.
Other scarce migrants trapped at the same site around the same time as this specimen were: 11/11/2025 – Spodoptera cilium (Dark Mottled Willow), 12/11/2025 – Diasemiopsis ramburialis (Migrant Sable); 13/11/2025 – Helicoverpa armigera (Scarce Bordered Straw)
Native to North and South America it is a long distance migrant. It was found in Africa in 2013 and is now widespread throughout the continent; it has also been found in India, SE Asia and Australasia. Records are increasing in southern Europe as a result of migration, but it is not yet considered to be established. Moth Dissection shows one undated Irish record but until publication of this St Mary's record it did not have a RES checklist number. The vernacular name "Armyworm" refers to the invasive behaviour of the larva which is a serious pest of several crops - hence the specific name "frugiperda" which means "lost fruit". It a notifiable quarantine pest and has been intercepted at UK customs on >100 occasions.
Other scarce migrants trapped at the same site around the same time as this specimen were: 11/11/2025 – Spodoptera cilium (Dark Mottled Willow), 12/11/2025 – Diasemiopsis ramburialis (Migrant Sable); 13/11/2025 – Helicoverpa armigera (Scarce Bordered Straw)
Spodoptera frugiperda (Fall Armyworm) §1 female (image provided by Will Scott)
ID: Sexually dimorphic particularly with respect to a broad white wedge at the costal end of the subterminal line and, which is only hinted at in the female; a small white spot in the dorsal portion of the kidney mark, which is not seen in the female; and the oval mark which is brown in the male and variable in the female. The female somewhat resembles an over-sized S.exigua (Small Mottled Willow). The hindwing of both sexes is white with a blackish terminal line extending along the termen from the apex but not reaching the tornus.
Male genitalia:
Female genitalia: The ovipositor and segment 8 have a dense covering of hair scales that need to be removed carefully to avoid damaging the underlying structures. The antrum is well-sclerotised; after a short hyaline gap distal to the antrum the remainder of the ductus bursae is well sclerotised to its junction with the corpus bursae; the corpus bursae is sclerotised in its posterior ⅓, but not in its anterior ⅔, with a sharp line of demarcation; the signum is rounded with longitudinal pleats.
Male genitalia:
Female genitalia: The ovipositor and segment 8 have a dense covering of hair scales that need to be removed carefully to avoid damaging the underlying structures. The antrum is well-sclerotised; after a short hyaline gap distal to the antrum the remainder of the ductus bursae is well sclerotised to its junction with the corpus bursae; the corpus bursae is sclerotised in its posterior ⅓, but not in its anterior ⅔, with a sharp line of demarcation; the signum is rounded with longitudinal pleats.
§1 St Mary's, Isles of Scilly; 12/11/2025; female; fw 17.2mm; to 125W mv light; specimen trapped and provided by Mick and Will Scott;
FIRST MIGRANT RECORD FOR BRITAIN
All images © Chris Lewis
FIRST MIGRANT RECORD FOR BRITAIN
All images © Chris Lewis
Page published 14/12/2025 (§1)
