Thymelicus acteon (Rottemburg, 1775)

Host plants:
The larva feeds on grasses, in Central Europe especially Brachypodium pinnatum. In the south the larvae use also other Brachypodium (e.g. B. retusum), but also other grasses like Dactylus (own larval records from Andalusia and Samos) and even Phragmites (larval records in Lesbos Island).

Habitat:
In Central Europpe Thymelicus acteon needs xerothermic, but often mild to moderate dense and higher growing grasslands in the lower mountain ranges (e.g. Jura) and in lowlands. Best is a mosaic of gappy or stony, low growing parts with loosely and single brachypodium pinnatum and the higher growing edges with denser Brachypodium facies in limestone regions. Thymelicus acteon is missing in the northern Alps.

In the south Thymelicus acteon can live in many types of habitat, including wetlands (e.g. along the coasts) and river valleys. I recorded many larvae on Brachypodium sylvaticum along rivers in the semi-shade of woodlands in Samos Island. In this island also hot garrigues and ruderal places are settled.

Life cycle:
The oviposition occurs in small numbers (3-15, often around 6-10 eggs) in leaf sheaths of grasses. The female lands on a blade and climbs backwards with searching abdomen tip 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 longer oval than the rounder eggs of T. sylvestris. The L1 larva with black head capsule (brown in T. sylvestris, also black in T. lineola) hatches a few days later (around 10 days), consumes the egg shell and creates directly the winter cocoon (hibernaculum) which it usually does not leave until spring. In the south the larvae start feeding sometimes already after the autumnal rainfalls so that larvae may be found also in winter in the lowlands there. The caterpillars are mature in May and June (in Central Europe) and can be easily found where Brachypodium pinnatum grows on more gappy ground and partly also in denser vegetated areas on the same square with those of Thymelicus lineola and Thymelicus sylvestris (observations on the Swabian Alb in Germany). The adults fly from late June or July to early September, in the south already from April.

Endangerment factors:
As species with a narrow ecological licence and a distinct restriction to nutrient-poor, extensively managed grasslands, Thymelicus acteon is endangered and in strong decline in many, especially northern regions. In southern Germany it declines dramatically at the moment, probably due to less grazing intensity and subsequent decline of the pastural grass Brachypodium pinnatum.

In the south Thymelicus acteon is still common and widespread.

Remarks:
The distribution extends from the Canary Islands (subspecies christi, partly regarded as a separate species, see in this taxon) across Northwest Africa and Central and southern Europe to western Asia.