Last modified: April 10, 2021, 10:19 a.m.
A rare species in Belgium. It was discovered in LG in the early 1960s and only at the beginning of the 21st century it spread out all over Flanders and the south, more than likely due to a better knowledge of its biology.
The mine initially starts as a long gallery which follows a vein or the margin of the leaf and later on it becomes an upper surface blotch. The larva broadens its mine continuously and applies a lot of spinning, turning the initial gallery into a blotch. The blackish frass is usually contained in the center of the mine, between the spinning.
The mine can easily be confused with the one of the diptera Calycomyza artemisiae (Agromyzidae), but the mine of this fly always stays flat while the one of S. omissella turns into a threedimentional blotch.
See also gracillariidae.net and bladmineerders.be.
A dull, ochreous cocoon.
Larvae can best be searched for in May–June and again in August–September.
Before pupation the larva leaves the mine. Pupation takes place in a dull ochreous cocoon spun on leaf litter.
The adults are active in late afternoon and later come to light.
The adults fly in two generations a year: in May and again in August.