Two-striped spring maiden
| Two-striped spring maiden | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Two-striped whitefly ( Cordulegaster boltonii ), male |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Cordulegaster boltonii | ||||||||||||
| ( Donovan , 1807) |
The two-striped spring damsel ( Cordulegaster boltonii ) is a very large dragonfly that occurs in clean, small running waters from the suborder of the large dragonflies (Anisoptera). It is characterized by narrow yellow stripes on a black base color. The species is considered endangered and is legally “specially protected” in Germany.
features
The image of the two-striped spring damsel reaches body lengths of around 85 millimeters in females, which even exceeds the largest species of dragonfly. The wings have spans between nine and eleven centimeters. As with all representatives of the source maiden, the eyes only touch at one point. The thorax is black with yellow antehumeral stripes and side bands. The abdomen ( abdomen ), which is also black, has yellow transverse bands, mostly interrupted in the middle, with a wider one in the middle of the segment and a narrower one at the rear edge of the segment. The coloring is about the same in both sexes. The occipital triangle at the back between the eyes is yellow. On the underside of the upper abdominal appendages ( cerci ) there is - in contrast to the similar striped swell maiden ( Cordulegaster bidentata ) - only one tooth.
Occurrence
Two-striped spring maidens live on mountain streams and sandy lowland streams with a very good water quality. Sometimes there are only narrow rivulets, while wider rivers are avoided. The area of the species extends from north-west Africa and the Iberian Peninsula across western and central Europe to Russia in the east and central Scandinavia in the north. There are three subspecies in the Mediterranean that can form mixed populations.
In Germany, Cordulegaster boltonii occurs scattered from the North German lowlands (e.g. Lüneburg Heath ) to the Alps . The main points of distribution and frequency are the water-rich edges of the low mountain ranges, in young moraine areas of eastern Germany also streams at terminal moraines and in glacial valleys .
Way of life
Larvae
The very large and powerful larvae , over 40 millimeters in length, live buried in the substrate of low-flow, vegetation-free sections of little or unpolluted streams and ditches. Quiet water spots in particular, such as those created by obstacles, scouring or sliding slopes in a stream meander , are populated. In addition, the larvae occur in the shallow edge areas of the spring channels of lime spring bogs, in small spring and sinter basins with tufa or in wet moss cushions. Depending on the biotope conditions and water temperatures, their development time is around three to seven, usually four to five years. The larvae are predominantly nocturnal, passive ambulance hunters who hide in the sediment, only look out with their eyes and prey on river fleas , mussel crabs , beetles and aquatic larvae of various insects. Even cannibalism between the dragonfly larvae occurs. When the water level drops, the larvae look for deeper water holes, crawl under stones, moss or fallen leaves or they burrow in the mud.
Adult animals
The adults hatch from the last larval stage in the early morning hours and directly on the bank, but occasionally the larvae move several meters away from the water. The exuvia are usually found with the head tilted slightly backwards on vertical or overhanging structures in herbaceous vegetation, on stones or on roots. While the hatched dragonflies mature, they fly away from the water in sunny spots (meadows, forest clearings).
Two-striped swell maids are not very persistent fliers. The males patrol up and down the populated bodies of water at a low altitude and after a few minutes settle on bank plants or branches. They have no fixed territories. The females can hardly be seen; they probably only come to the water to lay their eggs. The adult animals catch smaller insects for food. Their lifespan is estimated to be at least eight weeks.
The flight time in Central Europe is between the beginning of June and the end of September / beginning of October, with a focus on July and August. For reproduction, the pairs form the "tandems" and " copulation wheels " that are usual for dragonflies . The subsequent oviposition takes place in a peculiar way, only typical for Cordulegaster species. In an approximately vertical posture, the flying females literally plow the eggs into the substrate of the stream; they have a specially designed long laying apparatus for this purpose . The animal makes setting movements every one to two seconds, with some eggs being "inoculated" into the ground. As the laying apparatus is often pushed into the substrate, it wears out over time.
Taxonomy and nomenclature
The species was first described in 1805 by Pierre André Latreille as Aeschna annulata . However, this name was an invalid homonym, as the specific epithet annulata in the same genus had already been assigned by Johann Christian Fabricius in 1798 for an Indian species. The oldest valid name according to the rules of zoological nomenclature is Libellula boltonii , which was set up in 1807 by the British zoologist Edward Donovan (1768-1837) in volume 12 of the work The Natural History of British Insects . The species was later transferred to the genus Cordulegaster .
Donovan chose the scientific name of the species in honor of William Bolton (1722–1778) from Halifax (West Yorkshire) . Like his younger brother James Bolton, he was an avid amateur zoologist and collector of natural objects.
swell
literature
- Heiko Bellmann: The Kosmos dragonfly guide. Franckh-Kosmos, Stuttgart 2007, ISBN 978-3-440-10616-7 (Kosmos-Naturführer).
- Klaus Sternberg, Rainer Buchwald & Ulrike Stephan: Cordulegaster boltonii (Donovan, 1807), two-striped spring maiden. In: Sternberg / Buchwald (ed.): Die Libellen Baden-Württemberg. Volume 2: Dragonflies (Anisoptera). Ulmer, Stuttgart 2000, ISBN 3-8001-3514-0 , pp. 191-208.
Individual evidence
- ↑ www.WISIA.de
- ^ John Edmondson: James Bolton of Halifax: Pioneer Pennine Naturalist and Wildlife Artist. Liverpool 1995.
