White-shielded figwort scraper

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White-shielded figwort scraper
White-shielded figwort scraper (Cionus scrophulariae)

White- shielded figwort scraper ( Cionus scrophulariae )

Systematics
Order : Beetle (Coleoptera)
Subordination : Polyphaga
Family : Weevil (Curculionidae)
Subfamily : Curculioninae
Genre : Cionus
Type : White-shielded figwort scraper
Scientific name
Cionus scrophulariae
( Linnaeus , 1758)
Fig. 1: side view
Fig. 2: Mating

The white- shielded figwort scraper ( Cionus scrophulariae ) is a beetle from the family of weevils and the subfamily Curculioninae . The genus Cionus is represented in Europe with 39 species . Some of these look so similar that they can only be reliably differentiated through genital examinations .

The genus name Cionus is from Altgr. κίων kíon, kíonos for "column" derived and refers to the round trunk. The species name scrophulariae means that the species is found on the genus Scrophularia (figwort). However, there are other species of the genus Cionus that develop on Scrophularia .

The name “figwort scraper” expresses that the larva scrapes off the underside of the figwort's leaf during a certain development phase. The word "Weißschildig" is explained by the fact that the black seam spot on the wing covers is bordered in a shield-shaped whitish at the back. On the Internet, Cionus scrophulariae often only uses the name "Braunwurzschaber" without any additions. This obscures the fact that there are several types of brownwort scrapers.

The Weissshield Figwort scraper is widespread in Europe and common in Central Europe.

Characteristics of the beetle

The round beetle is 4.5 to five millimeters long, making it larger than the similar Cionus tuberculosus . It is covered with differently colored scale hairs that form a grid pattern on the wing covers. The likelihood of confusion is great (image web links 2.)

The trunk is long, relatively thin, round and slightly curved downwards. As with almost all weevils, the antennae are kneeled and arise in the front third of the proboscis. The shaft link of the sensor can be inserted into the sensor pit. This arises on the trunk side and runs straight down to the lower edge of the eyes. The long shaft member is followed by a five-membered antenna whip, the first two members of which are elongated, the following are short. The curled, elongated and pointed club of four limbs is attached to the scourge. The eyes approach each other on the forehead, the forehead between the eyes is significantly narrower than the trunk.

The dense white or whitish hairy neck shield is offset stehkragen like front narrow and behind the front edge. It is arched and significantly narrower than the elytra together. A black elongated spot on the midline of the pronotum does not reach its front edge. In Cionus tuberculosus, on the other hand, there is a dark, broad, continuous midline.

From above, no part (no epimers) of the mid-breast is visible between the pronotum and the wing covers. The rear breast is not only partially but completely covered in light hair.

The wing covers are slightly longer than wide, and together unlike Cionus tuberculosus arched only moderately. They appear spotted in black and white due to the dense and close-fitting hair. The type of stain distinguishes the Weißschildigen Braunwurz scraper from similar species (image web links 1). On the wing cover seam in front of the center there is a noticeable, velvety black spot (sutural blemish), which is trimmed back by a white to yellowish spot. A second, smaller black suture spot at the end of the wing-coverts is bordered at the front by a white to yellowish scale spot. The wing covers are divided into longitudinal strips by rows of dots . The rows of dots can only be seen clearly when the hair is shaved off, the stripes are defined by the spaces between the rows of dots. The first gap (at the wing cover seam) runs in an arc around the front seam spot and is black and white latticed in front of and behind it. The third, fifth, seventh and ninth spaces are slightly raised and also black with white grid points. The second, fourth, sixth and eighth spaces are uniformly blackish gray haired and flatter than the odd spaces.

The abdomen is mainly finely haired with black hair on the underside, the rear sternites have light patches of hair (image web links 5). The rear edge of the second to fourth sternite is drawn back on the side.

The front hips are touching. The thighs are moderately club-shaped and have a tooth in front of the tip. The straight rails are unreinforced. The claws that have grown together at the base are clearly of unequal length in the male, the difference is less clear in the female.

larva

The larvae are surrounded by a slime coat and therefore resemble slugs (pictures web links 3 and 4). The head capsule measures 0.26-0.30 millimeters across in the first larval stage, 0.42-0.44 millimeters in the second, and 0.70-0.74 millimeters in the third and last.

cocoon

The cocoons are slightly transparent, round brownish bubbles that are quite firm (image web links 6). In the inflorescence or fruit cluster, they are usually attached to a fruit stalk and resemble fruit pods. The cocoon has point-like openings 20 to 60 micrometers in diameter with outwardly frayed edges. These openings are relatively close at the bottom and at the sides, but scattered irregularly, at the top they are rare. The cocoon itself is not water-repellent but impermeable and the edges of the holes prevent water from entering. The cocoons have a length of 5.7 millimeters with a deviation of 0.25 millimeters and a thickness between 4.16 and 4.84 millimeters.

egg

The pale yellow, shiny eggs are 0.85 millimeters long with a deviation of 0.05 millimeters. With the same deviation, the transverse diameter averages 0.45 millimeters.

biology

nutrition

The larvae live on different species of the genus Scrophularia (figwort family), exceptionally also on Verbascum and the introduced buddleia , and are therefore classified as oligophagous . They eat different parts of the plant at different stages of development. The adults eat the leaves and stems of the host plant (image web link 2).

The beetles and larvae eat during the day and night, but are more intense in both at night.

Biotope

The beetle is extremely moisture-loving. Depending on the location of the host plants, it occurs in damp meadows, in streams and river meadows, in damp places in the interior and on the edge of deciduous forests and on the banks of ditches and streams. Despite this relatively high degree of specialization, it competes with several closely related species. The time and part of the plant when the eggs are laid and pupated are different for each species.

development

Except in the first larval stage, the larvae live freely on the host plants. They are covered with slime to protect themselves from predators. This mucus is produced in the back of the midgut and excreted through the intestine. Before pupation, the production of mucus is switched to the production of chitin threads, from which the pupa cocoon is made. Pupation does not take place in the ground, but the larvae attach the cocoon to the host plant in the area of ​​the inflorescence. The doll is almost transparent at first. If the humidity is too low, the development cannot be completed successfully.

The following data relate to a study on the host plant Scrophularia nodosa in Schleswig-Holstein . The animals overwintered as imago did not appear until late spring, early June to mid-July. They carry out a ripening process of a few days. The males are probably attracted to the females by pheromones . The male scans the female with the feelers. Then it rises on the wing covers of the female. If the female is not ready to mate, she shakes her abdomen vigorously until the male lets go. If the female allows mating (Fig. 2), copulation can take up to thirty minutes. Soon after, the female begins to lay eggs, which takes place exclusively in developing flower buds. To do this, the female gnaws an elongated hole as deep as the trunk allows. Part of the ovary is removed. Then the female turns and lays four to nine yellowish eggs in a hole that has been made recently. Then the hole is closed with a secretion, feces, or a mixture thereof. The closure is initially soft and transparent, then within a day it becomes hard and turns dark green or brown in color. The female needs two to three hours for the entire process. Usually only one egg is laid per bud. The larvae hatched from the egg in the laboratory at 20 ° C after six to eight days.

The first larval stage feeds inside the bud. It took four to six days in a laboratory test at 20 ° C. Later the larva gnaws its way out and continues to eat sitting on the outside of the sepal. Initially, only the surface of the underside of the leaf is scraped off, leaving out the leaf veins . The second larval stage lasted only two to four days in laboratory tests. In the third larval stage, veins and central ribs of leaves, flowers, young fruits and the stalk are also gnawed. Larvae that gnaw the buds and the seed heads change their color to reddish-brown or purple. They eat large holes in the leaf blade and destroy almost all fruits of the infected plant. Some infested plants will later produce new fruits that contain only a few seeds.

The third larval stage lasted four to ten days at 20 ° C. Mature larvae of the third instar collect in the upper parts of the plant. They lose their mucous covering so that the individual body segments can be recognized for the first time. You start by making the cocoon. Up to 35 cocoons were found in the inflorescence of a plant. The doll rests upside down in the cocoon. The imago hatched in the laboratory after nine to thirteen days. The hardened adults bite a circular opening at the lower end of the cocoon with their mandibles, possibly being assisted by chitin-dissolving enzymes . The lid pops off and the imago slips. The newly hatched adults can be found from mid-July to mid-August. The larva therefore took five weeks to develop in the laboratory, and around 6 weeks are given for animals living in the wild. The number of newly hatched animals showed a clear maximum in July. Beetles encountered in early July may be the last to hibernate or the first newly hatched adults.

Migration behavior

In a study on migration behavior, two animals were found in fifty marked animals after one week at a distance of 100 meters, one animal had moved 300 meters after four weeks. Although the animals can fly, the tendency to spread is low. Even with a dense infestation of a plant, nearby plants are not infested.

Natural enemies

Larvae are violently attacked by the sociable hymenoptera Entedon zanara . It was also observed that the pupae in the cocoons were attacked by the polyphagous parasitic wasp Scambus buolianae .

distribution

The species is common in large parts of Europe . In Scandinavia it is only reported from Norway . No data are available from Portugal , the Benelux countries and some Eastern European countries. It is also represented in the Middle East and Asia . After North America , the species has been introduced and is undergoing expansion.

literature

Individual evidence

  1. ↑ a b Cionus scrophulariae in Fauna Europaea. Retrieved February 7, 2012
  2. ↑ Cionus at Fauna Europaea. Retrieved February 7, 2012
  3. ↑ Sigmund Schenkling: Explanation of the scientific beetle names.
  4. ↑ Cionus tuberculosus in Fauna Europaea. Retrieved February 9, 2012
  5. ↑ Edmund Reitter : Fauna Germanica, the beetles of the German Empire , Volume V, KGLutz 'Verlag, Stuttgart 1916
  6. ↑ a b c d e f g h i j Martin Räther: "Notes on four weevils in the tribe Cionini (Coleoptera: Curculionidae) associated with Scrophularia nodosa (Scrophulariaceae), Part I" Bonn.zool.Beitr. Vol. 40 Issue 2, pp. 109–121 Bonn, July 1989
  7. ↑ a b George Dimmock: "The cocoons of Cionus scrophulariae " Psyche Volume 3 (1882), Issue 103-104, Pages 411-413 doi : 10.1155 / 1882/93068 as PDF
  8. ↑ Klaus Koch : The beetles of Central Europe . Ed .: Heinz Freude . tape 3 : ecology . Goecke & Evers, Krefeld 1992, ISBN 3-87263-042-3 .
  9. ↑ Heinz Freude , Karl Wilhelm Harde , Gustav Adolf Lohse (ed.): Die Käfer Mitteleuropas (=  Käfer Mitteleuropas . Volume 1 : Introduction to Beetle Science ). 1st edition. Goecke & Evers, Krefeld 1965, ISBN 3-8274-0675-7 .
  10. ↑ JN Tristram: "The peritrophic membrane and cocoon ribbons in larvae of Cionus scrophulariae " Journal of Insect Physiology Vol. 24, Issue 5, 1987, pp 291-398
  11. ^ Adolf Horion : Käferkunde for nature lovers . Vittorio Klostermann, Frankfurt am Main 1949
  12. ↑ Entedon zanara at Fauna Europaea. Retrieved February 9, 2012
  13. ↑ Scambus buolianae at Fauna Europaea. Retrieved February 9, 2012
  14. ↑ Arnett, RH, Jr., MC Thomas, PE Skelley and JH Frank: American Beetles, Volume II: Polyphaga: Scarabaeoidea through Curculionoidea CRC Press LLC, Boca Raton, FL, 2002, ISBN 0849309549

Web links

Commons : Cionus scrophulariae  - collection of images, videos and audio files