Lutrochus
| Lutrochus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the family | ||||||||||||
| Lutrochidae | ||||||||||||
| Kasap & Crowson , 1975 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Lutrochus | ||||||||||||
| Erichson , 1847 |
Lutrochus is the only genus of the family Lutrochidae from the order of the beetles (Coleoptera). The genus includes about 15 species that are found in the New World, from the southern United States to Brazil.
features
Beetle
The beetles are 3.0 to 6.0 millimeters long and 1.7 to 3.0 millimeters wide. Its body is oval in shape, its back is strong, its sides are only slightly curved. The body surface is glossy dark brown in color, dense and evenly structured and dense, fine, close, golden hairs. The hairs are a little longer on the belly side. The mouthparts on the head are directed downwards (hypognathic), the head is partially retracted into the prothorax and therefore cannot be fully recognized when viewed from above. It is almost as wide as it is long. The top of the head (epicranium) has an upside-down "Y" -shaped groove. The compound eyes are not protruding and densely hairy. They are roughly faceted . The sensor deflections are visible from above. The frontoclypeal suture is straight and can sometimes hardly be seen. The frontal plate ( clypeus ) is curved, narrow, membranous in front and densely hairy behind. The sclerotized labrum is also oblique, converges backwards, and has a curved front edge. It is broadly rounded on the side. Its rear surface is densely short and hairy long, the front part is bald. The epipharynx is membranous. Seen from above, one can see the enlarged front side areas, which are provided with long, curved hair. The front edge of the epipharynx is densely covered with hairs of different lengths and shapes. The short antennae are eleven segments. They are positioned next to the frontoclypeal suture between the eyes and the anterior branches of the “Y” -shaped groove on the epicranium and do not reach the rear edge of the head. The antennae are densely covered with short hairs. The scapus is about the same length as the flagellum , has a spherical base and is hairy on the outside. The pedicellus is almost rectangular and as wide as the scapus and as long as the third to fifth antennae segments combined. It is just as long hairy on the outside, its flagellum is narrower than the scapus. The mandibles are symmetrical and have a hem with elongated hairs and a three-tooth point on the outside. The two chewings of the maxilla , the lacinia and the galea, are bipartite and well defined. The first limb of the galea, the basigalea, is small and almost rectangular, the second limb, the distigalea, is wide and almost trapezoidal. She wears a thick tuft of short hair on top. The lacinia is elongated and has a lateral tuft of hair dorsally at the tip.
The trapezoidal pronotum is curved. The upper wings are very punctiform and heavily covered with hair. They have their widest extent in the first half and are about 1.1 to 1.4 times as long as they are wide. Their ends are slightly tapered. The epipleurs are broad in the basal third, otherwise they narrow. They are indented at the level of the middle and rear legs. The second pair of wings (alae) have an open radial and anal cell. The hips ( coxes ) are densely hairy, those of the front and rear legs are curved and furrowed to accommodate the thighs ( femora ). The middle hips are rounded. The rails are also curved, hairy, and grooved to accommodate the rails ( tibia ). The rails of the front and back legs are very hairy, the middle rails have a few isolated long hairs, their distal part is hairy. The tarsi are sparsely hairy.
The abdomen has five ventrites (visible abdominal sclerites ), which are the third to seventh, whereby the second and third sternite can also be fused. The large third sternite is pressed flat at the base to accommodate the hind legs. Functional stigmas are formed on the eighth segment of the abdomen . The female ovipositor is well developed.
Larvae
The larvae are four to ten millimeters long and one to two millimeters wide. Their bodies are similar to wireworms . The head, the tergites on the thorax and abdomen are heavily sclerotized and dark brown in color, as well as being very pointy and hairy. Short feather-like hairs can be found between longer hairs. The mouthparts are directed forward (prognath) and visible from above, partially retracted into the prothorax. It is slightly wider than it is long and has rounded edges. There are five pairs of point eyes ( ocelli ) laterally on the upper side, one pair being shifted towards the abdomen, close to the base of the mandibles. The face plate (clypeus) is trapezoidal with weak hair on the sides. The antennae are tripartite, glabrous, and have elongated, tubular segments. The first segment is longer and wider than the second, the third is short and has a few sensory hairs at the tip. The severely sclerotized short mandibles are symmetrical. They have a tip with three teeth and one or two more teeth near the tip. The hypopharynx is hairy on the front.
The back of the top of the thorax has a row of hairs of different sizes. The prothorax is almost as long as the meso- and metathorax combined. In the Neotropic species , a line of thread-like hair is formed near the front edge of the pronotum. The meso- and metanotum each have a row of short, feather-like hairs in the front area. A pair of round spiracles are located on the front side of the mesothorax. The legs are short and strong and all look similar. All segments are hairy short.
The abdomen tapers evenly from front to back. The back of the first to eighth abdomen segment has a dense line of short, feathery hair in front. In the neotropical species, the bases of the hair are almost adjacent to each other and form a groove. The back of the segments has tufts of hair. The ventral side of the first to eighth abdominal segment is hairy and has a strong point-like structure. The tergum is connected to the sternum from the fourth to the eighth abdominal segment . In the nearctic species, the size of the pleura decreases from the first to the fourth abdominal segment. The ninth segment of the abdomen is elongated and flattened, with the sternum connected to the tergite. The segment is hairy on the sides and back. Urogomphi are absent. The tenth abdomen segment forms an operculum that can be folded in on the abdomen and is connected to the ninth abdomen segment by a thin membrane. The rear edge is hairy, the back has a pair of strong, curved claws. On the first to the eighth abdominal segment there are lateral spiracles in front.
Doll
The pupae are approximately 7.2 millimeters long and, including the wing sheaths, a maximum of 2.7 millimeters wide, with the widest point being on the first abdominal segment. The pupae are free pupae and have their extremities and wings protruding freely. They are elongated, hairless and mostly whitish in color. The head is almost completely covered by the prothorax. The pronotum is almost trapezoidal in shape and has wavy side edges and a pair of thread-like appendages on the front. The abdomen tapers backwards, its first to eighth segment is curved, the ninth segment is elongated and triangular. There is a curved sclerotized band on the rear of the back of the first to seventh abdominal segments. The spiracles are located on small appendages on the first to fifth abdominal segment.
Occurrence and way of life
The beetles live aquatic or semi-aquatic and colonize shallow rapids with a stony, sandy or sandy / muddy bottom, in streams with clear water, with a high calcium content. In Brazil, however, specimens of Lutrochus germari have also been found in streams with varying levels of calcium. Some individuals have also been found in streams that drained carbonate soils, granite rocks, or gneiss that had a pH between 7.2 and 6.0. Both larvae and adults of Lutrochus germari have been found in rotting wood, the pieces of wood being of different sizes, but always lying under water. Adults and larvae of most species can be found in cracks of rotting dead wood. Beetles can also be found on deadwood on the surface, and larvae can also be found in the wood of softwood shrubs.
The adults stay in the water permanently under the surface and transport an air bubble with their body hair. They usually rest motionless, but quickly seek a dark hiding place when exposed to sunlight.
Systematics
The genus Lutrochus was originally assigned to the family of the hook beetle (Dryopidae), later it was counted to the Limnichidae . Roy Crowson eventually recognized the family's monophyly , which is based on the characteristics of the larval abdomen. In them, the sternites and tergites are fused on the fourth / fifth to eighth segment. The association of the family within the byrrhoidea is confirmed by the folding of the wings , which is of the hook beetle type, and the shortened anterior appendage of the metendosternite of the imagines located in the middle of the metathorax .
supporting documents
Individual evidence
- ↑ a b c d e f g h i j Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 , p. 508 ff . (English).
literature
- Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 (English).