Small blue arrow
| Small blue arrow | ||||||||||||
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Small blue arrow - Orthetrum coerulescens, mating wheel. Taken on Schwarzbach in Wöllnau, Doberschütz, Saxony, Germany. |
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| Scientific name | ||||||||||||
| Orthetrum coerulescens | ||||||||||||
| ( Fabricius , 1798) |
The Little Blue Arrow ( Orthetrum coerulescens ) is a type of dragonfly from the family of the sail dragonflies . It is the smallest species of blue arrow found in the German-speaking area. The second part of the scientific name means “to turn blue” or “bluish” and aims at the process of changing the color of the males as they mature. Except for the northeast, the species is distributed across Europe. The habitat of the Kleiner Blaupfeils is mostly characterized by slowly flowing meadow streams or ditches with not too great a depth of water; gravel pits are also seldom settled. Bodies of water with heavy vegetation at the edges are preferred. The small blue arrow is ecologically very demanding and is one of the regionally endangered species.
features
Imago
The Little Blue arrow is a relatively small bubble, the abdomen ( abdominal ) in the males reached a length of 25-31 millimeters. The females here measure 26 to 30 millimeters. The body of young adults is yellowish light brown. On the sides of the chest ( thorax ) there is a light pink shade. The seams of the chest are brownish and Antehumeralbinden white and black berändert. The abdomen is veiled lemon yellow with brown and black bands. In addition, the entire wings of the female are yellowish, while the male is only the base. After a few days of life, the yellowish color of the wings disappears in both sexes and the wings become transparent. The hind wings reach 28 to 33 millimeters in the males, 28 to 31 in the females. The pterostigma measures 3.2 to 4 millimeters in the males, 3.5 to 3.8 millimeters in the females. In the case of the males, when the wings become colorless, the rest of the body is tinted. At first the abdomen turns slightly pink, with the previously black areas turning bluish. The blue then spreads to the entire abdomen. The thorax takes on a reddish brown color and shows blue stripes in very old males. The color of the female remains essentially brown-yellow, but can also change to olive-brown. The wings are not as clear here as with the males and still suggest a bit of yellow.
larva
Like the adults, the larvae also undergo a color change. The larvae that have just hatched from the egg are still light gray and only measure around 1.2 millimeters. The sides of the head, antennae and legs are dark gray, the eyes black. As the larva develops, it turns a uniform golden brown or golden gray, with the exception of the black wing sheaths . There are small dorsal spines on segments four through seven of the abdomen . However, these are often hidden by the hair that is also present. There are very small crooked lateral spines on the eighth and ninth segments. In the last larval stage, the animals measure 16.5 to 18.5 millimeters.
At first glance, the larvae are to be confused with those of the flat belly ( Libellula depressa ). In addition to the fact that the larvae of the small blue arrow are significantly smaller, a distinction is also possible via the narrow abdomen typical of blue arrow pills.
Way of life, reproduction and development
The Little Blue Arrow likes to sit in sunny, not too high places, while calmly folding its wings forward. The males are very faithful to their chosen seat and sometimes return to the same seat for days after each flight. If a male sees one of the significantly more mobile females, it lands on his thorax and connects to it. The pairing then takes place in the pairing wheel and takes between 5 and 120 seconds. The pairing wheel usually lands, but not always. After copulation and a short rest period at the side of the male, the female flies to the water followed by the male and shakes off the eggs by touching the surface of the water.
The yellowish white eggs, 0.5 to 0.6 × 0.35 to 0.37 millimeters in size, turn brownish-orange over time. The larvae hatch after five to six weeks. Their development time is estimated at two years.
swell
literature
- Robert, Paul-A. (1959): Die Libellen (Odonaten) - Authorized translation by Otto Paul Wenger [p. 300ff], Kümmerly & Frey, Geographischer Verlag, Bern.
- Dreyer, W. (1986): Die Libellen - The comprehensive handbook on the biology and ecology of all Central European species with identification keys for adults and larvae [p. 88], Gerstenberg Verlag, Hildesheim, ISBN 3-8067-2022-3
- Sternberg, K. & R. Buchwald (2000): Orthetrum coerulescens (Fabricius, 1798) - Kleiner Blaupfeil. Pp. 506-523. In: Sternberg, K. & R. Buchwald (eds.): Die Libellen Baden-Württemberg. Volume 2: Dragonflies (Anisoptera). Ulmer, Stuttgart, ISBN 3-8001-3514-0
Web links
- Orthetrum coerulescens inthe IUCN 2013 Red List of Threatened Species . Posted by: Clausnitzer, V., 2007. Retrieved February 22, 2014.
- Little Blaupfeil in Lower Saxony - profile and distribution