Thymelicus sylvestris (Poda, 1761)

Host plants:
The larvae feed on productive grasses such as Dactylus, Agropyron, Calamagrostis, Avena or Phalaris and very often Holcus species. In slightly disturbed humid grasslands near Memmingen (S-Germany) I recorded many ovipositions and eggs on Holcus lanatus. On that grass species I found also T. lineola, but much rarer.

Habitat:
Thymelicus sylvestris inhabits wetlands, fens, clearcuts, nutrient-poor grasslands and (woodland) fringes. The imago also flies in xerothermic grasslands on limestone, where it is often syntopic with the other two species of Thymelicus. In southern Europe Thymelicus sylvestris often also inhabits ruderal areas with grasses like Avena, even very dry and hot ones.

Life cycle:
The oviposition occurs in small numbers (3-18, often around 10 eggs) in leaf sheaths of productive grasses. The female lands on a blade and climbs backwards with searching abdomen tip and helically downwards. If there is a suitable gap between the blade and a leaf sheath the eggs are deposited. The eggs are not visible from the outside. They are rounder than the still more oval eggs of T. lineola and T. acteon. The L1 larva with brown head capsule (black in T. lineola and T. acteon) hatches a few days later (around 10 days), consumes the egg shell and creates directly the winter cocoon (hibernaculum) which it does not leave until spring. The young larva is less conspicuous than that of Th. lineola (probably as it lives more near the dround on less conspicuous grass leaves) and I thus found it more rarely. The larvae live in typical tubes of grass leaves and cause a typical feeding pattern.
I observed, however, older caterpillars numerously in late May and early June. At this time they may also live on seat pads more openly on grass leaves.
Thymelicus sylvestris tends to be the earliest appearing Thymelicus in Central Europe and flies there between mid June and early August. In southern Europe, it is on the wing from late April to June, only in the mounatins later.

Endangerment factors:
Thymelicus sylvestris is not endangered.

Remarks:
The distribution ranges from Northwest Africa across Europe (except northern Scandinavia and some islands of especially the western Mediterranean and Crete) to the Middle East.