005 Stigmella betulicola

NEPTICULIDAE | Nepticulinae | Nepticulini

04.005 Stigmella betulicola (Birch Dot)

ws: 4-5mm; bivoltine May, Aug; mine Jul, Sep-Nov; birch (Betula spp); locally common throughout GB

Stigmella betulicola (?) §1 female

ID: From the key in MBGBI1 - Forewing with white non-metallic fascia, without other pale spots; terminal cilia not abruptly white; fascia distal to midwing > 5 species which are distinguished as follows: S.malella - dividing line in terminal cilia; S.tityrella - purplish-fuscous fascia proximal to white fascia; S.microtheriella - forewing deep purplish fuscous (lighter bronzy-fuscous in the remaining 2 species); S.glutinosae - fascia slightly distal to midwing; S.betulicola - fascia well distal to midwing. The descriptions (p259&260) gives: collar leaden fuscous in ♂ and ferruginous in ♀ S.betulicola and ochreous-white in both sexes of S.microtheriella. This would seem to provide a more absolute means of distinguishing the species and suggests that §1 is S.microtheriella - except that images at Moth Dissection labelled as S.betulicola show a white collar. The descriptions also state that the apical area is darker purplish fuscous in all 5 species. (The listed flight seasons suggest that none of these species fly in June when §1 was obtained).
Female genitalia: Images are available at Moth Dissection for 4 of these 5 species (not S.malella). From these images it appears that the signa of S.betulicola are relatively short (occupying ~⅓ the length of the corpus bursae) while those of S.microtheriella are relatively long (occupying ~½ the length of the corpus bursae). The image right shows S.microtheriella on the left, S.betulicola on the right with lines indicating the lengths of the signa as they appear from left to right in the image. Although this matches the images shown at Moth Dissection, I need more experience to increase confidence over these identifications.

Variation
Dissection
Male genitalia
Female genitalia

Page published 21/12/2020 (§1)