35.114 Scrobipalpa instabilella (Douglas, 1846)

One of the more variable species with external features which can be very similar to S. salinella, occasionally S. nitentella and some forms of S. samadensis. There are a few similar additional species found just across the channel in France which would be well worth looking out for - for further information see under S. salicorniae.

Because of the sometimes considerable variation within most saltmarsh inhabiting Scrobipalpa species, identification by wing markings alone will often not be possible. Caution and care are the watchwords for this group.

If a moth has been bred from a known foodplant, and therefore also time of year when the larva feeds and the nature of its feeding methods have been observed, this information, plus a freshly emerged moth, will allow the number of possibilites to be reduced considerably. If the bred or caught moth is a fresh specimen AND displays the distinctive markings of some species (see below) then an identification without more detailed examination should be possible in many cases.

Those more readily identifiable when freshly emerged by the forewing markings are listed below. However all of these also have variation in their wing markings which, when the obvious features are obscured or worn, will then resemble some other Scrobipalpa species.

Scrobipalpa suaedella - those with an obvious clear pale ochreous dorsal quarter to the forewing.

Scrobipalpa obsoletella - those with the forewing a pale greyish colour lacking any red-brown colouration and appearing paler in the final one-third due to a pale postmedial fascia.

Scrobipalpa ocellatella - those with the prominent angled fascia at three quarters on the forewing and dark markings contrasting with the surrounding paler ground colour.

In cases where there is any doubt, particularly where worn light-trapped specimens are concerned, dissection will be essential to obtain an accurate identification until a good familiarity is built up with the range of species and their markings at a particular site.

Genitalia differences are often small but reasonably constant between the various species. It has been noted that the apical arm on the tip of the aedeagus of S. instabilella can vary slightly in width and the angle made at the end sometimes only reaches c.75 degrees rather than the full 90 degrees of most specimens.