Paradiarsia punicea (Hübner, [1803])

Host plants:
The larvae are polyphagous in the herb layer. According to literature Rubus species (R. idaeus, caesius, fruticosus agg.) are favoured. I cannot confirm this. In autumn I found larvae under e.g. Filipendula ulmaria and Valeriana officinalis which showed strong feeding scars. Rubus species missed at this place. Generally, there should be no dependency on a special plant, but the larvae use a quite broad spectrum of herbs and grasses, occasionally probably also low-growing shrubs. Filipendula ulmaria, however, may be one of the more important host plants at least before hibernation.

Habitat:
Paradiarsia punicea inhabits a broad variety of wetlands. The exact requirements are a contentious issue. But according to literature it seems so that the larvae use somewhat drier places with considerable shrub encroachment within these wetlands. Paradiarsia punicea is reported from small birch clear-cuts in moorlands, from bushy woodland aisles in humid, open forests, riparian woodlands and similar places. Near Munich Paradiarsia punicea has been recorded also near urban places, but the larval habitats are not reported there. But you won't go astray in supposing relict riparian woodlands or bushy landscapes there, too.

In southern Germany (Allgäu, 800 m above sea level) I recorded larvae along a small rivulet with some young black alder (Alnus glutinosa) in October 2020. This rivulet was bordered by a Carex-dominated, nutrient-poor fen meadow on one side and by a Molinia-fen with young spruce plantation on the other. Accompanying species have been Lycaena helle, Boloria titania, B. eunomia and Melitaea diamina. The larvae have been recorded only in the direct vicinity of the rivulet (at its shore area) under and between Filipendula ground leaves, grasses an other herbs near the ground. The site was rather semi-open to open than wooded. In the vicinity some pine bogs exist.

In November 2021 and in September 2022 I recorded several larvae in a rich in willow fen between spruce forest and open Molinia fen meadow near Isny (Baden-Württemberg). There the larvae have been found in quite wet and moderately nutrient-rich forb fringes with Filipendula ulmaria, Geum rivale, Angelica sylvestris and others on the edge of the willow scrub. Bogs are found there, too, in some hundred meters of distance.

Thus Paradiarsia punicea is not a real bog dweller, but settles more in not too nutrient-rich edges in fens or riparian environments with a certain portion of shrubs. If the edges are too rich in nutrients and felted (e.g. nettles), I found not a single larva so far. But bogs are in many (but not all) cases scattered around the habitats. Paradiarsia punicea is found up to about 1000 m only.

Life cycle:
The larva hibernates in the penultimate instar. On 11. October 2020 I recorded 11 larvae. 10 have been already in the penultimate instar, one small larva still two instars earlier. The larvae hided in the ground vegetation during daytime and could be beaten. The conspicuous bright, orange-brown colour lasts for about three instars from late summer to spring, but the exact number of moults is varying. In mild weather they feed well into November and hibernate then. The development is rapid in spring between March and early May. After the last moult the larvae become dark blackish brown in ground colour.
The moths occur between late May and July or even early August with peak in the second half of June. They can be atrracted with light and bait. The young larvae should be active from late July.

Endangerment factors:
Paradiarsia punicea is heavily endangered in central Europe. The main reason is as usual destroyment or decline in quality of habitat. Large-scale moors and open riparian woodlands have become scarce due to dense afforestation with dark tree species like spruce or beech, dewatering measures with subsequent agricultural intensification, succession and overgrowth, fertilization, transfer into arable land or overbuilding (infrastructure, urbanization etc.). Paradiarsia punicea strongholds have been pushed back to a few regions with larger portion of suitable habitat like the northern edge of the Alps in Bavaria. But even there Paradiarsia punicea is very local. Obviously it needs large-scale habitats because only a very small portion of most habitats is actually usable by the larvae due to their complex requirements.

Global warming may have a negative influence on these relic populations, too.

Remarks:
Paradiarsia punicea occurs from central Europe (from eastern France) to east Asia (northern Japan). In central Europe it is usually very scarce and a bit more widespread (but regionally already extinct also there) only from central Switzerland across westernmost Austria and southern Baden-Württemberg to southern Bavaria. Otherwise it is found for example from NE-Germany across parts of Poland eastwards.

Literature:
Malicky, Hans (1961): Paradiarsia punicea Hb. .- Zeitschrift der Wiener Entomologischen Gesellschaft 46: 146-150, 153-160, Tafel 12.

Ströbl, Alois (1965): Zur Kenntnis von Paradiarsia punicea Hb, (Lepidoptera, Noctuidae).-Nachrichtenblatt der Bayerischen Entomologen 14: 61-74.