Stigmella zelleriella

Diagnostic description: 

Diagnosis.  Male specimens of zelleriella and S. benanderella are  very similar but the latter is usually smaller, more coarsely scaled and  lacks purplish lustre on forewing apex.  The genitalia are easily separable  by the shape of uncus and valvae.  Females of zelleriella, S. benanderella  and S. floslactella are similarly coloured; benanderella can be separated  from zelleriella by smaller size and blunt abdominal tip; floslactella is  more coarsely scaled and has more contrasting wing pattern with blackish  wing apex and contrasting yellowish white cilia.  The shape of the apophyses  provide good separating characters; long and broad in zelleriella, long and  very slender in floslactella and short in benanderella.

Morphology: 

Male. Wingspan: 5.2-5.8 mm.  Head: frontal tuft grey-brown,  sometimes mixed with yellow; collar yellowish white; scape white to pale  grey; antenna three fifths of forewing length, dark grey.  Thorax concolorous  with base of forewing.  Forewing: area proximal to fascia shining pale to  dark grey-brown with bronze reflections; fascia absent or, if present, ill-  defined greyish; distal to fascia slightly darker, brownish with more or  less distinct purplish lustre; terminal cilia yellowish grey beyond an ill-defined line of dark-tipped scales, paler grey at tips.  Hindwing and cilia  pale yellowish grey.  Abdomen dark grey with small grey anal tufts. 
Female. Wingspan: 4.5-6.2 mm.  Frontal tuft varying  from yellowish white to ochreous or orange, sometimes mixed with brown but  lighter than in male; collar and scape yellowish white; antenna half length  of forewing.  Forewing area proximal to fascia yellowish bronze to pale  yellow; fascia ill-defined, slightly paler than basal half of forewing;  distal to fascia distinctly darker than basal part, brownish to dark grey  with purplish lustre.  Abdomen grey with prominent, long and pointed  ovipositor; anal tufts pale grey, as long as ovipositor. Male genitalia.  Vinculum with shallow to moderately  deep anterior emargination.  Uncus almost square at tip, medially split  into two lobes, each lobe slightly emarginate.  Gnathos with prominent  basal plate; horns long and parallel, well separated at base; lateral arms  and anterior processes distinct and well sclerotized.  Valva long, parallel-  sided, posteriorly rounded with two very short inward-curved points. Transtilla with short, broad transverse bar and triangular sublateral  processes.  Aedeagus distinctly shorter than genital capsule with 5 to 6  unilaterally more sclerotized cornuti and a cluster of 5 to 9 spines of  varying length; number of cornuti and spines 10-15, usually 12. Female genitalia. Corpus bursae with broad and  conspicuous band of scallop-like chitin plates and a few, very fine and  indistinct pectinations; posterior part (ductus bursae) narrow, strongly  folded.  Ductus spermathecae with fine internal spines.  Apophyses very  long, anteriores broad, medially fused; anterior processes broad,  inward-curved; posterior apophyses almost as long as anteriores, slender.  Anal tufts two thirds length of apophyses.  Ovipositor very long, tip  pointed.

Associations: 

Host plants:  Salix repens and S. arenaria, in northern Sweden and Finland mainly on Salix lapponum and possibly other Salix species.  Egg:  is laid on underside of leaf, close to midrib or leaf margin.  Larva: yellow  to brownish yellow.  Mine : starts as a short gallery,  often following leaf-margin and terminating in a blotch occupying half the  leaf, more in small leaves; frass black almost completely filling the  gallery; irregularly dispersed in the blotch.  Vacated mines stain black.  Mines probably not reliably separable from benanderella mines and sometimes  occurring together;  however, mines with the egg on the leaf upperside always  belong to benanderella.


Distribution: 

Denmark: NEZ and several localities in Jutland; Norway: Sti.;  S. Sweden: Gtl., Hall. and S. Finland; widely distributed in northern Finland  and Sweden, south to Idre in Dlr. -  Along the coast of The Netherlands,  Belgium, Poland and S. England, probably also in N. Germany.

Life cycle: 

Voltinism:  in Denmark and the Netherlands bivoltine.  Larvae found from late June to first half of July and from late September to  early October; in northern Scandinavia in August.  Outside Fennoscandia the  species is almost confined to coastal sand dunes.


Citation: 

Description based on Johansson and Nielsen (1990)

Notes on description: 
A long series of more uniformly coloured specimens from inland localities in northern Sweden have been regarded as a species separate from S. zelleriella: Nepticula lappovimella Svensson, 1976: 204. Van Nieukerken (1983a: 59) synonymized lappovimella with S. zelleriella. This synonymization was rejected by Svensson (1985: 71, 78). Material from northern Finland, reared from Salix lapponum and S. repens show practically no differences from the southern form of zelleriella. As S. zelleriella (including lappovimella) shows approximately the same geographical variability as most other NW European Stigmella species, and as no other differences which justify a separate specific status for lappovimella are found, we are of the opinion that S. lappovimella must be regarded as of lower rank than species. See also, Introduction and group description. Lectotype of N. zelleriella designated by van Nieukerken (1983a). Bruun (1987) showed small differences in wingscale morphology between northern and southern Scandinavian populations of zelleriella and suggested this demonstrated zelleriella and lappovimella to be valid species. Their distribution was subsequently mapped (Bruun, 1988). We remain unconvinced that the variation is not clinal within a single species, but obviously renewed examination of the problem is required.
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