Status of S. w-album in Denmark

By  Martin Bjerg, Sdr. Banevej 3A, 5.tv., 3400 Hillerød.


The article describes a breeding of Satyrium w-album, Knoch from Danish populations. The eggs are easily found near buds of Ulmus glabra and the larvae are easily kept on branches in water. The larvae feeds in flowers and seeds and pupation takes place on branches of the foodplant. The pupae is easily recognised due to the hairy look. In Denmark, as in many other countries, the Dutch Elm Disease is a serious threat to the populations of S. w-album as most of the old elm trees have died. The author describes the finding of a caterpillar of S. w-album on oak (Quercus robur). The ova was actually laid on the oak and the larva was bred entirely with oak and gave a fine male. However this finding is regarded as a random case. Most likely will populations of w-album in Denmark survive on buds of young elm-plants, but the w-album population will suffer severely from the elm disease. 

IMG0022.jpg (12011 bytes)The egg of  Satyrium w-album Knoch is usually placed near a flowerbud and is easily recognised by its   "UFO" shape. (Foto: S. Johansen)
IMG0024.jpg (11298 bytes) Low. left. The small larvae is extremely well camouflaged among the elm flowers. (Foto: S. Johansen)
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Fully grown the larvae is abt. 15 mm long and easier to find. In this stage it is also able to feed on leaves of elm. (Foto: S. Johansen)
IMG0023.jpg (10524 bytes)The pupae is often placed on a small branch and fastened with silk. It differs from the pupae of the other hairstreaks by the hairs. (Foto: P. Stadel Nielsen)
IMG0026.jpg (8798 bytes)A rarely beautifull specimen of  Satyrium w-album Knoch. The tails on the hindwings are often auickly lost. (Foto: J. Meulengracht-Madsen)



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Fig. 2. Old gigant elm trees as this one north of Copenhagen, is now a rare sight. Unfortunately it is also the major habitat for Satyrium w-album Knoch. (Foto: S. Johansen)