Scorpion flies
| Panorpidae | ||||||||||||
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Common scorpion fly ( Panorpa communis ), male |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Panorpidae | ||||||||||||
| Linnaeus , 1758 |
The scorpion flies (Panorpidae) are a family of the beak flies (Mecoptera) that occurs in around 100 species worldwide. In Central Europe only five species of the genus Panorpa can be found, including Panorpa communis with a body length of about 18 millimeters.
Features of the scorpion flies
The scorpion flies have, like all other beak flies, a trunk-like elongated head (picture) with chewing-biting mouthparts . The maxilla and the labium are elongated at the base. The four large, net-like veined and often darkly spotted wings are laid flat in the resting position and slightly spread backwards. The scorpion flies show a pronounced sexual dimorphism . The males have a clearly thickened genital segment at the end of the abdomen, which is usually carried curved upwards and is reminiscent of the sting of a scorpion . It contains a gland that produces a sex pheromone . In addition, there are a pair of forceps on the ninth abdomen segment and extensions on the third and fourth abdomen segment. In the female, the end of the abdomen is pointed and is used as a laying tube.
Way of life of the scorpion flies
In summer, the scorpion flies are mostly in shady areas, often on bushes. They feed mainly on dead and injured insects, sometimes also on nectar , fruits such as raspberries or honeydew from aphids . Various species are described as also eating insects that are trapped in the webs of spiders ( kleptoparasitism ). For this purpose they balance on the spider threads and are able to detach themselves from sticky threads with the help of their own midgut juice. It has not yet been clarified why the scorpion flies are not attacked by the spiders, which notice the visit to their web and often first approach the scorpion fly.
Reproductive behavior
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The reproductive behavior of scorpion flies has been particularly well researched. For the Central European species P. germanica , P. alpina and P. cognata it could be proven that the males release pheromones in order to attract females ready to mate. The male specimens of P. vulgaris , which do not produce pheromones, are an exception . The females are attracted to the male by the pheromone produced in the abdominal gland, with a range of about eight meters. The female sits down on the substrate and the male approaches it with a conspicuous waving of its wings and a typical up and down movement of the abdomen. The latter creates a substrate sound that is registered by the female through sensory hair on the legs. When willing to mate, the female reacts with the same movement, but often the female moves away a little by flying up briefly, whereupon the male approaches again.
The male can now use three different types of copulation strategies:
- If the female is obviously ready to lay, she offers a dead insect, which the male also defends against rivals.
- If the female is not yet ready to lay, the male gives her several saliva globules as a gift, which he has previously formed in the salivary glands. It can produce and transfer seven pellets one after the other. These are eaten by the female during copulation and the female does not behave aggressively.
- Rape is also possible.
It has been proven that the handing over of mating gifts has a clearly positive effect on the female's egg production, probably due to the additional food resources that the female received from the male. Copulation itself begins with the male grasping the female with the abdominal forceps and the two of them then remaining in a V-position for about 15 to 20 minutes. Another wedging takes place over the wings. A pair can mate several times in a row and mating is also possible while the female is eating.
The female lays the eggs a few days after mating with the stretched abdomen in loose soil. The eggs are glued together to form balls. A female lays several clutches.
Larval development
The larvae of the scorpion flies are similar in appearance to caterpillars and are dark in color. They have eight pairs of short stumpy feet on the abdominal segments and bristles on the back that sit on warts. They live in tunnels in the ground and feed mainly on the carrion of dead insects or other small animals, but also on real meat or plants. With four flap-like structures on the anus , they can attach themselves to the floor and straighten up.
In the species Panorpa communis there are four larval moults, pupation takes place in burrows. This species forms two generations per year, the second generation hibernates as larvae that are ready to pupate.
Species in Central Europe
The distinction between the individual scorpion fly species is mainly based on the development of the sexual organs and the shape and relative size and shape of the abdominal segments.
- Panorpa alpina Rambur, 1842: first longitudinal artery of the fore wing running parallel to the front edge merges with the front edge approximately in the middle
- Panorpa cognata Rambur, 1842: wing drawing light brown / pale, in males the rear edge of the 6th abdomen segment with a humped curve
- Panorpa communis L. , 1758: mostly a continuous black wing band. The spot on the base of the wing extends over a wing cell, sometimes it is absent.
- Panorpa germanica L. , 1758: no continuous black wing band, male has a hump on the 3rd abdominal segment
- Panorpa vulgaris Imhoff & Labram, 1836: the spot on the base of the wing extends over two, sometimes three wing cells.
The separate species status of P. communis and P. vulgaris is controversial and is not understood by all entomologists . However, Sauer and Hensle (1977) showed in a laboratory experiment that Panorpa communis and Panorpa vulgaris are "good" biological species . Both species are reproductively separated from each other by both progame and metagame isolation mechanisms .
Progame mechanisms:
- Seasonal separation: If both species occur syntopically , P. vulgaris appears two to three weeks before P. communis , which means that the main breeding times of the two species are around this period apart. This results in a reduced probability that sexually mature animals of both species will meet.
- Microclimatic niche: P. communis occurs mainly in damp and shady locations, while P. vulgaris prefers sunny and dry locations, which also reduces the probability of inter-species contact.
Metagame mechanisms:
- Larval mortality: matings between P. vulgaris and P. communis brought about in the laboratory led to copulations in around 20 percent of cases , but larvae hatched from the resulting clutches in only 0.03 percent of cases. Of these, in turn, none survived the fourth instar.
Panorpa communis and Panorpa vulgaris are therefore also genetically isolated, since no reproductive hybrids can arise.
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Individual evidence
- ^ Nicole Aumann: Life history and mating system of the scorpion fly Panorpa communis L. (Mecoptera, Insecta). Dissertation University of Bonn, 2000, online as PDF ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (375 kB)
- ↑ Insects Saxony. Retrieved July 14, 2019 .
- ↑ Insects Saxony. Retrieved July 14, 2019 .
literature
- Klaus Honomichl & Heiko Bellmann: Biology and ecology of insects . CD-ROM, Gustav Fischer Verlag, Stuttgart 1994, ISBN 3-437-25023-X
- Sauer, KP & Sommersell, M .: Influence of the males on the fitness of the females of Panorpa vulgaris (Mecoptera, Panorpidae) . Rat. Dtsch. Zool. Ges. 81 , 1988, p. 261
- Sauer, KP, Hensle, R. (1977): Reproductive isolation, ecological segregation and morphological difference of the twin species Panorpa communis L. and P. vulgaris Imhoff and Labram (Insecta, Mecoptera). Z. f. zool. systematics u. Evolutionary Studies , 15 : 169-207
- David Grimaldi & Michael S. Engel: Evolution of the Insects. Cambridge University Press, New York 2005 ISBN 0-521-82149-5
Web links
- http://www.naturspektrum.de/spezies/panorpa_communis.php Information and license-free photos