Saw beetle
| Saw beetle | ||||||||||||
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| Heteroceridae | ||||||||||||
| MacLeay , 1825 |
The saw beetles , scientific name Heteroceridae , are a family of beetles within the superfamily Byrrhoidea . They are common worldwide. In total there are about 300 species in 15 genera , of which three genera with 21 species occur in Central Europe. Larvae and adults live on vegetation-free banks of water ( semi- aquatic ).
features
They are small beetles about 1 to 8 millimeters long. The body is somewhat elongated, oval, slightly flattened and covered by thick, fine hairs. The females are usually larger and more compact than the males ( sexual dimorphism ). The beetles are dark in color, usually with a clear pattern of red or yellow spots and dots. The construction of the antennas is striking and responsible for the naming . These are nine or eleven limbs and short. All links with the exception of the first three form an externally sawn (serrated) club. The head is stretched forward (prognath) with large mandibles protruding above the head , the complex eyes are present but relatively small.
The prothorax is shorter than it is broad and rounded transversely oval. On the ventral side, a protrusion (prosternal process) protrudes backwards, where it engages in a pit in the mid-chest. The legs are usually transformed into tombstones , the rails ( tibia ) somewhat widened with long rows of thorns on the outside. The tarsi are narrow and delicately built with five segments. The elytra are elongated with parallel side margins and completely cover the abdomen. As far as is known, all species can fly.
Six sternites (the second to the seventh) are visible on the abdomen , the second and third sternites are fused. The rear sternites have long hairs pointing backwards.
Larvae
The larvae are elongated, cylindrical and about 2 to 11 millimeters long. They are predominantly whitish in color with dark brown, platy sclerites on the back and a brown head. The head is directed forward and somewhat flattened, the labium and maxilla form a shovel-shaped complex protruding forward. The head has very short, three-part antennae and five larval eyes (stemmata) on both sides. The five-limbed legs, especially the front legs, have been transformed into grave legs. The larva has open spiracles on the mesothorax and abdomen and is air-breathing .
Way of life
Beetles and larvae live in the bank region of water bodies. They dig long, winding, tunnel-like galleries in bare, moist sand or silt. The tunnels are horizontal and are just below the surface so they are often visible from above as sinuous lines. They are usually branched. The beetles dig the tunnels by scraping away the loose material with their forelegs up and back while pushing the body forward at the same time. The tunnels are feeding passages, not living tubes or buildings, they are not permanently inhabited. Under unfavorable conditions, v. a. if the sand gets too dry, the beetles burrow to the surface and run or fly to a new spot. The beetles can fly off extremely quickly even in the event of disturbances, which is why catching them is not very easy.
In addition to the banks of ponds or rivers, the animals also appear in mud flats and marshes on the seashore, but they avoid direct contact with salt water and leave their habitat in storm surges to seek protection inland. When flooded, the animals stay dry due to their water-repellent ( hydrophobic ) hair.
The diet is not fully understood. The larvae, and to a certain extent also the adults, simply eat the entire substrate and then digest the organic components. Single-cell algae, especially diatoms , should be important for the nutrition of adults in particular .
Systematics
The saw beetles belong to a family group within the Byrrhoidea that only includes families with aquatic larvae. This group has been described as "Dryopoidea". They are divided into two subfamilies:
The following genera have been identified in Europe:
- Micilus . The only European species is Micilus murinus .
- Heterocerus
- Augylus
literature
- Sergio A. Vanin, Cleide Costa, Sergio Ide, Rolf G. Beutel: 18.6 Heteroceridae. In: Rolf G. Beutel & Richard A. Leschen (editor) Handbook of zoology. Volume IV. Arthropoda: Insecta. Part 38. Coleoptera. Volume 1: Morphology and systematics, Archostemata, Adephaga, Myxophaga, Polyphaga partim. Berlin, New York: Walter de Gruyter.
- P. Aguilera, A. Mascagni, I. Ribera (1998): The family Heteroceridae MacLeay, 1825 (Coleoptera, Dryopoidea) in the Iberian peninsula and the Balearic Islands. Miscellania Zoologica 21 (l): 75-100.
Individual evidence
- ↑ George R. Clark II and Brett C. Ratcliffe (1989): Observations on the Tunnel Morphology of Heterocerus brunneus Melsheimer (Coleoptera: Heteroceridae) and Its Paleoecological Significance . Journal of Paleontology Vol.63, No.2: 228-232.
