Phylum Arthropoda (Arthropods) ➔ Subphylum Hexapoda (Hexapods) ➔ Class Insecta (Insects) ➔ Order Coleoptera (Beetles) ➔ Family Chrysomelidae (Leaf beetles)
Plagiosterna aenea (Linnaeus, 1758)
Erzfarbener Erlenblattkäfer
Synonyms and other combinations:
Chrysomela aenea Linnaeus, 1758 | Chrysomela coeruleoviolacea De Geer, 1775 | Melasoma bicolor Schilsky, 1908 | Chrysomela fuscicornis Fabricius, 1781 | Chrysomela haemorrhoidalis O.F. Müller, 1776 | Chrysomela violacea Olivier, 1790 | Coccinella vitellinae Scopoli, 1763 |
Classification:
Plagiosterna aenea belongs to the subfamily Chrysomelinae, tribe Chrysomelini.Distribution:
Europe (except Scandinavia), in parts of Asia.Habitat:
In alluvial forests, brook valleys and at water margins on alders.Description:
Length 6.5 - 8.5 mm; body metallic green, red-gold or blue; elytra much wider than the pronotum, with strongly set off lateral bulge, disorderly dotted; pronotum without well set off lateral bulge, dotting of the pronotum in the middle slight, at the sides coarser and uneven; tibiae at the outer rim with imperfect furrow; 3rd segment of tarsi weakly cut out at the tip.Plagiosterna aenea is the only species of the genus Plagiosterna in Europe.
Biology:
Plagiosterna aenea lives on different alder species. Host plants in Central Europe are black alder (Alnus glutinosa), grey alder (Alnus incana) and Alnus alnobetula.The adults of Plagiosterna aenea appear at the end of April from their winter shelter and start feeding on the leaves of the host plants. They are macropter and able to fly, but rarely fly. The yellowish eggs are laid by the females in small groups of about 25 - 30 eggs on the undersides of the leaves. After approximately 7 days, the larvae hatch. They pass through 3 larval stages in 18 - 22 days. The larvae feed in the first days in the group and spread later individually on the leaves. The adult larvae attach themselves to a leaf with the rear end for pupation. The pupal stage lasts about a week. The new beetle generation hatches in July/August. The entire development takes about 5 weeks. The beetles undergo a maturation feeding period of about 2 weeks, retreat from mid-August to undergo a long autumn and winter diapause. They usually spend the winter in forests at dry places in the leaf layer.
The species normally forms one generation per year in Germany. In climatically more favourable locations in Southern Europe, 2 generations can also be passed through.
Note:
The pictures from 2013 show a pupa of Plagiosterna aenea and the beetle with the empty pupal shell hatched 3 days later. Shortly after hatching the beetle, which was still predominantly light with dark pronotum, legs and antennae, changed colour and showed its final metallic blue basic colouring only 4 hours later.The last instar larva found in 2019 was in a hurry to grow up. Only 4 days after it had freed itself from last larval skin, the metamorphosis to the adult beetle was completed.
References, further reading, links:
- Rheinheimer, Joachim, & Hassler, Michael: Die Blattkäfer Baden-Württembergs, 2018, 928 pages, Kleinsteuber Books (Karlsruhe), ISBN 978-3-9818110-2-5
- Arved Lompe: Die Käfer Europas - Ein Bestimmungswerk im Internet
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