Last modified: Feb. 27, 2021, 4:29 p.m.
A very rare species in Belgium, thus far (2020) only known from the northeastern part of the country. Contrary to e.g. Cameraria ohridella, another invasive gracillariid species, Ph. issikii does not spread fast over the rest of the country, though its larval hostplant is readily available almost everywhere. Intensive searches in the center, the south and the west of Belgium have not resulted in any positive observation.
Invasive In Belgium since October 2011.
Discovered as mines on Tilia cordata at Zutendaal (LI), leg. S. Wullaert. Established in the northeastern part of Belgium but thus far (2020) absent elsewhere. The species originates from Japan and some other countries in the East Palaearctic. It was probably introduced into eastern Europe in 1970 and from there it spread gradually towards the west.
Dimorphic species: the summer generation has a brownish ground colour while the autumn generation is much more greyish, sometimes even dark grey. Like in many other Phyllonorycter species the whitish pattern is present, but rather indistinct, especially in the greyish form.
Not unicolorous as most Phyllonorycter larvae but partly yellowish and partly whitish.
Rather flat tentiform mine at the onderside of a leaf. Sometimes more mines on one leaf, and in such cases, the leaf is more contorted. Full developed mines are easily seen from the upperside as light greyish patches. Frass is concentrated in a corner of the mine and seen as black patches inside the mine.
See also gracillariidae.net and bladmineerders.be.
Dark brown pupa.
The species has a preference for the lower branches of Tilia trees of which the leaves are more in the shadow. Hibernation in the cocoon of the second generation among leaf litter on the ground. It has been observed, however, that from collected mines in October some adults emerge, indicating that the species might, at least partially, hibernate in the adult stage as well.
Two generations a year: May and August.