Mediterranean field cricket
| Mediterranean field cricket | ||||||||||||
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Mediterranean field crickets at Bristol Zoo |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gryllus bimaculatus | ||||||||||||
| De Geer , 1773 |
The Mediterranean field cricket , Mediterranean cricket or Zweifleckgrille ( Gryllus bimaculatus ) is an insect from the family of real crickets (Gryllidae) and, as the name suggests, occurs in the Mediterranean region.
features
The crickets are about 20 to 33 millimeters long and are therefore slightly larger than the field crickets ( Gryllus campestris ). Her head is also smaller than the pronotum . They have two yellowish spots at the base of the forewings ; the basic color of the animals is black. The hind wings are fully developed and protrude beyond the forewings and the abdomen , when at rest they are folded lengthways. The animals are usually quite capable of flying, at least over short distances.
Occurrence
The Mediterranean field cricket occurs from the Iberian Peninsula to Greece and lives near the sea coast. In some places, e.g. B. in the southern French dune areas, they are common. They appear in their area from July to September.
Way of life
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The Mediterranean field crickets do not build their own passages, but have their hiding places under stones and other objects lying on the ground. There is a hierarchy in social coexistence, which is carried out through battles. Animals closer to rank fight more often than animals whose ranks are further apart in the structure.
Stridulation and acoustic communication
Acoustic signals play an important role in social and mating behavior. They proceed from the sexually mature males, because only these have sound-producing stridulation organs. The most common and conspicuous song is the common or enticing song, which is used to attract females ready to mate. It consists of sequences of mostly four individual sound events in rapid succession, which are separated from one another by intervals. The lure chant represents the chirping familiar from crickets. There is also a rival chant with which males fight over territories, as well as the advertising chant, which is part of the mating behavior.
Stridulation organ
The fore wings of sexually mature males are on average 15.23 mm long, the hind wings 20.78 mm long. The information applies to the right wing; there are no statistically significant differences between the right and left wings, nor are there any differences in length between the wings of the male and female.
The chants of the males are based on structures of the dorsal field of the forewings, which are formed in the same way on both wings. Starting from the base of the wing, this is the shrill charger, a section of which, the shrill strip, is covered on the underside with shrill teeth (lamellae). The number of shrill teeth averages 134.9 teeth per shrill bar. The shrill edge is located on the inner edge of the wing and next to the shrill strip. Towards the rear end of the wing, the harp (diagonal field), the round mirror and finally the anal field, which is characterized by irregular, small veins, follow the shrill veins. At rest, the dorsal field of the right wing lies above that of the left wing and almost completely covers it.
With this arrangement, when chirping, the shrill strip of the right wing brushes the shrill edge of the left wing. The identical and fully developed singing sets on both wings led to the opinion that the males use these sets at will and sing both with the right wing over the left and in the reverse position. According to the results of the experimental review, this is not the case. In 30 males who had been singing in the normal position for a long time (right wing above the left), the wings were carefully folded. After just 2-3 minutes, at the latest after 30 minutes, 27 test animals had restored the normal position. In a further experiment, the wings of 20 males were already folded 2–3 hours after the last moult, when the wings were already unfolded but not yet or just colored. Half of these males retained the anomalous position of the wings throughout their life and chirped. Their lure singing was much quieter than normal singing males, they no longer uttered their rival singing. If females ready to mate had a choice, they preferred males with unchanged wing positions. The other test animals restored the normal position of the wings or changed several times between the two positions over the course of a few days.
Development of the shrill teeth
The formation of the shrill teeth only takes place towards the end of the last larval stage. At this stage the development of the wings is already well advanced. Because of their size, they lie folded in the skeletal sheaths of the larva’s wings. Only the part in which the shrill strip is created is not folded. Here, lamellar cells and intermediate cells that alternate with one another differentiate. A lamella (shrill tooth) is created from each lamella formation cell. During the imaginal moult, the wings and thus also the shrill ridges are stretched to their final shape. As a result, both cell types degenerate, first the lamellar cells, then the intermediate cells as well.
Keeping in captivity
The Mediterranean field cricket is often used as a feed insect for terrarium animals . Rapid reproduction and undemanding make them one of the most frequently fed species. It can be handled safely with bare hands, as the animals neither sting nor bite painfully.
Individual evidence
- ↑ a b c Anna Alfonsa Stark: Investigations on the sound organ of some crickets and grasshopper species, at the same time a contribution to the right-left problem . Zoological Yearbooks, Department of Anatomy 77, pp. 9–50, 1958.
literature
- Anna Alfonsa Stark: Investigations on the sound organ of some crickets and grasshopper species, at the same time a contribution to the right-left problem . Zoological Yearbooks, Department of Anatomy 77, pp. 9–50, 1958.
- Heiko Bellmann: Der Kosmos Heuschreckenführer, The types of Central Europe safely determine , Franckh-Kosmos Verlags-GmbH & Co, Stuttgart 2006, ISBN 3-440-10447-8
