Vinculum
1/ short, triangular, with convex margins.
4/ often tapered rather abruptly into long, slender saccus; nethertheless, saccus shows a great variability in shape, especially in freyerella, perhaps due to geographic variation. For this reason its shape is not always a good diagnostic feature.

Saccus
1/ narrow, blunt with slightly swollen tip; slender and long.
2/ more slender

Vinculum
1/ broad

Saccus
1/ wide, which is widest just before blunt tip; rather short and broad.
2/ stouter

Valva 1/ broadening distally

Spine 1/ shorter, distinct

Valva 1/ of almost equal width throughout its length

Spine 1/ longer, very distinct

Aedeagus
2/ stouter (this appears to be wrong)
3/ slender, curving slightly from the base to the distal end

Aedeagus
2/ more slender (this appears to be wrong)
3/ Aedeagus more robust than freyerella character- istically bent one-quarter from the distal end.
4/ almost straight, and only its short apical part is slightly curved.

There are problems trying to sort this pair out via the genitalia and the adult should always be carefully preserved. The table below gives information of the genitalia given in various books and papers on the subject*. The most reliable feature appears to be the shape of the aedeagus and this should always be isolated during prep.
Considerable variation can be introduced during the prep stage, especially whilst attempting to ‘flatten’ the genitalia, which can cause the valva to twist and appear broad, tapered or thin, and to the vinculum/saccus, which can appear thin in some specimens and broader in others. Breaking apart the genitalia (as mentioned in MBGBI) might give more consistant results.

*Distilled from:
1/ The Elachistae (Lepidoptera) of Fennoscandia and Denmark Fauna Entomologica Scandinavica volume 6 (1977) by E. Traugott-Olsen and E. Schmidt Nielsen
2/ MBGBI vol. 3
3/ Revision of European Elachistidae (Lepidoptera, Elachistidae). The genus Cosmiotes Clemens, 1860 by Umberto Parenti and Pier Giuseppe Varalda in Boll.Mus.reg.Sci.nat.Torino vol. 20 - N2.
4/ Elachista baltica Hering, 1891 sp. rev. - a valid species of Elachistidae from the Baltic shore (Lepidoptera: Gelechioidea) by Tomasz Baran and Jaroslaw Buszko. Entomol. Fennica vol. 16 9 - 18.