Stigmella viscerella, Stigmella

Diagnostic description: 

Diagnosis.  S. viscerella is very similar to most other Stigmella  species without fascia and spots, particularly the species of the sanguisorbae  group.  The genitalia of viscerella differ widely from those of all European  Stigmella species.  The male genitalia are characterised by the long inner  lobe and the prominent curved process on the inner side of the valva.  The  female genitalia can be separated from those of all other unicolorous  Stigmella species by the combination of long and narrow ductus bursae and  vestibulum and large, oval corpus with dense cover of pectinations. 

Morphology: 

Male. Wingspan: 4.2-4.8 mm.  Head: ochreous to fuscous; tuft  on vertex often slightly paler; scape and collar whitish or yellowish  white; antenna approximately half length of forewing.  Thorax concolorous  with base of forewing.  Forewing: faintly shining bronzy brown, towards  apex dark with faint purple tinge; terminal cilia brownish but silvery grey  at tips.  Hindwing: greyish brown.  Abdomen fuscous. 
Female.  Wingspan: 4.8-4.9 mm.  Antenna markedly shorter than half  length of forewing.  Otherwise similar to male. Male genitalia. Vinculum with broad and shallow to  distinct emargination in anterior margin; corners short and subtriangular.  Uncus with pair of distinct, triangular projections.  Gnathos with prominent  rectangular plate formed by transverse bar and anterior processes and with  long outwardly-curved horns.  Valvae widely separated from each other;  with long and narrow inner lobe reaching almost to tip of distal process;  innerside of valva with long and slender, hook-like process; setae on  dorsal part of valva with minute lateral branches over almost entire length.  Transtilla without distinct sublateral processes.  Juxta broad and almost  square, united with tip of aedeagus and inner surface of valvae by a membrane;  juxta anteriorly articulates with ventral corners of valvae.  Aedeagus  about half as long as genital capsule; vesica with posterior hook, 25-35  small spines and at least 50 very small ones; cathrema very wide and  prominent. 
Female genitalia. Bursa copulatrix approximately fourfifths length of abdomen.  Accessory sac small, rounded, with small,  indistinct reticulate field at base.  Corpus bursae oval, densely  covered with pectinations.  Ductus spermathecae narrow with few  convolutions.  Apophyses anteriores distinctly shorter than posteriores.

Associations: 

Host plants:  Ulmus spp.  Egg: on upperside.  Larva: bright  green.  Mine : a gallery mine which starts with three or more  half circles around the egg site followed by a rather short part, often  following a rib, normally with at least one U-bend; mines on leaves exposed  to sun are much shorter than those on shaded leaves; frass coiled, completely  filling at least the first half of the mine.  Cocoon: leather brown.  

Distribution: 

Not in Scandinavia and Finland. - Widely distributed  in England and central, southern and southeast Europe.  Extremely local in  The Netherlands.

Life cycle: 

Voltinism: univoltine in northwest Europe, and bivoltine in southern Europe. 


Citation: 

Description based on Johansson and Nielsen (1990)

Notes on description: 
The Japanese species S. nakamurai Kemperman & Wilkinson appear to be very similar to viscerella in both colour pattern and genitalia.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith