Pine Resin-gall Moth Retinia resinella
Wingspan c.16-22 mm.
Retinia resinella is fairly common in much of England, but more so in Scotland where it can be abundant in places.
Larvae of this species have a two-year development period, beginning by boring into a small twig of the foodplant pine (Pinus), usually Scots pine, P. sylvestris. This causes the host plant to exude resin, which then forms a gall inside which the larva lives. In the second year the gall is enlarged and can be quite noticeable.
Pupating inside the gall, the adults then emerge in June. Because of the two-year cycle, moths are commonest in odd years.