White-spotted iris weevil

White-spotted iris weevil
White-spotted iris weevil on the flower of an iris with clearly visible feeding holes
Systematics
Order : Beetle (Coleoptera) Subordination : Polyphaga Family : Weevil (Curculionidae) Subfamily : Ceutorhynchinae Genre : Mononychus Type : White-spotted iris weevil
Scientific name
Mononychus punctum album
( Autumn , 1784)

The white-spotted iris weevil or iris weevil ( Mononychus punctumalbum ) is a beetle from the family of weevils and the subfamily Ceutorhynchinae . The four to five millimeter large beetle is often found on the swamp iris . It is easy to recognize by its rounded shape and the white point on the wing cover seam .

The species is listed in the red lists of North Rhine-Westphalia and Thuringia under category 3 (endangered).

Fig. 1: male Fig. 2: females Fig. 3: Bottom
Fig. 4: side view Fig. 5: Front view Fig. 6: brown form
Fig. 7: Hind tarsus	Fig. 8: from the front
Fig. 9: Loophole	Fig. 10: Beetles in a doll's cradle
	Fig. 12: Detail from the top, colored on the right ; turquoise: pronotum , yellow: epimer of the mid-breast, red: middle right leg, ocher: wing-coverts
Fig. 11: Doll

Notes on the name

It was first described in 1784 under the name Curculio Punctum album by Herbst . The detailed description also contains the sentence: “There is a white point on the right in the middle of the seam”. This explains the species name punctumalbum ( Latin púnctum "point" and álbum "white"), as well as the part "white point" of the German name. The part of the name "Iris weevil " refers to the host plant of the weevil.

The species, variants or local varieties have been described several times, the names exist:

• Curculio pseudacori Fabricius , 1792
• Curculio pseudacori Rossi , 1790
• Mononychus caucasicus Kolenati , 1859
• Mononychus euphraticus Schultze , 1897
• Mononychus salviae Germar , 1824
• Mononychus spermaticus Becker , 18625
• Mononychus syriacus Redtenbacher , 1849

In particular, the two variants of the species were regarded as separate species, M. pseudacori and M. salviae , respectively .

The genus name Monónychus is from Altgr. μόνος mónos, "only" and όνυξ, όνυχος ónyx, ónychos, "claw" derived and denotes that the second claw of the claw pair is stunted on the legs. The genus is represented worldwide with only three species, all of which also occur in Europe.

Characteristics of the beetle

The iris weevil has a spherical to short oval shape. As with almost all genera of the subfamily Ceutorhynchinae , the chitin plate (epimer of the mid-breast, colored yellow on the right in Fig. 12) above the abdominal plate of the mid-breast is drawn upwards and visible from above, where the rear outer corners of the pronotum meet the base of the wing covers bump.

The body is black, the antennae yellow-red, the club darkened. The head, side of the pronotum and the underside of the female (Fig. 2) are sparse, while the male (Fig. 1) has more extensive yellowish-gray to ocher-yellow scales. In the variation salviae (Fig. 6), the entire upper side has a dense, uniform ocher to brown scales.

The trunk is of medium length, thin and moderately curved downwards. It can be placed in a recess between the widely separated front hips (Fig. 3). The furrow to accommodate the proboscis is sharply defined and extends over the front and mid-chest. The front part is particularly noticeable because the bright scales are interrupted on the right and left. The twelve-link antennae are pivoted to the side halfway along the trunk. They are short, thin and sparsely haired. The first link (shaft link) is relatively short for the subfamily. It can be placed in the feeler pit that runs on the trunk from the point where the feelers are turned towards the lower front edge of the eye. The first limb of the flagellum is long and conical to pear-shaped, longer and stronger than the following six limbs. The second flagella is about the same length as the first, but significantly slimmer. The following four limbs are noticeably shorter. The last four antennae are fused into a compact and pointed club with a tiny last link. The eyes are rounded and slightly arched. The forehead is indented, at the level of the forehead the edges of the eyes are correspondingly higher than the center of the head (Figs. 4 and 5).

The upper jaw , which is exposed because of the missing upper lip, ends in two large teeth, on the inside there is another tooth at the base. The lower jaws form a large hairy ark. The jaw probes arise near the end of the lower jaw and are four-limbed, the last limb is tiny. The lip buttons are short and tripartite. The basal phalanx is shorter than it is wide and has two bristles. The middle link is cup-shaped, the end link tiny. The label is pointed triangular.

The pronotum is wider than it is long and narrows towards the front to almost the width of the head. The leading edge is simple. The base of the pronotum is triangularly widened towards the back of the label (Fig. 12). The pronotum is dotted with dense wrinkles . It has a clear, longitudinally shining central groove.

The wing covers are striped with dots. The stripes are scaly, the spaces between them are flat, almost in rows. The wings are pressed in behind the label. The shoulder angles are rounded, as are each wing-cover end. On the sunken wing cover seam there is a mostly clearly formed white spot, which the species name punctumalbum says. The label is recessed and barely visible.

The legs are strong. As the generic name Mononychus stating the jaw member carrying tarsi only one claw (Fig. 7). This is a big exception within the beetle. Under the third tarsal link there is a dense cushion of white hair, which improves the adhesion to the ground. The rails have a tooth-like elevation above the tip; a row of spiked bristles runs from this to the tip (Fig. 7).

biology

The moisture-loving species can be found on swampy and muddy banks, in damp stream and river meadows, in swamps and breaks, and occasionally in gardens, almost exclusively on the host plants.

The beetles produce only one generation per year. The female lays the eggs almost exclusively in the young fruits of the swamp iris . Occasionally, other types of iris are also used to lay eggs. In contrast, other plant species than the swamp iris are used more frequently as feeding plants.

The adult beetles overwinter. They swarm in May or June when the irises bloom. They look for the inflorescences of their host plants. In the sun they are very lively and gnaw different parts of the flower. The young fruits are also gnawed when the beetles prick them with their proboscis. Often these feeding holes sit in a row next to the longitudinal seams that connect the three chambers of the capsule fruits. These seams are raised in bulges and enable the beetles to hold on to them by riding on them. The plants react to the damage from the feeding holes by separating a sticky sap. This seals the feeding holes. The sap hardens on the surface and turns dark in color, so that the opening of the feeding passage becomes visible as a dark brown point.

After mating, eggs begin to lay, which extends over a longer period from July onwards. To lay the eggs, the thick, fleshy pericarp is completely pierced with the proboscis and the flat seeds, arranged like rolls of money, are gnawed on. The eggs are then placed in the seeds with the fold-out laying tube. The egg-laying hole closes quickly so that the eggs can develop well protected. Several eggs can be laid in one fruit. The total number of eggs laid is comparatively small. The hole for laying eggs is outwardly indistinguishable from a feeding hole.

The legless white larvae develop rapidly. Even before the seeds ripen, infected seeds can be recognized by their premature browning. Towards the end of its development, the larva has also eaten the neighboring seeds. The seeds are often eaten up except for a ring. The pupae's cradle usually extends over three adjacent seeds. The middle one is ring-shaped, the two adjacent ones cup-shaped. Soon beetles already hatched from eggs laid early, pupae from eggs laid later (Fig. 11) and larvae in the fruit at the same time.

The hatched beetle quickly discolours in the pupa cradle (Fig. 10). Around the time the fruits of the irises turn yellow (late summer), the first beetles begin to leave the pupa cradle. At the latest when the fruits burst open and the ripe seeds are released, all beetles have gnawed a hole in the open (Fig. 9) and left the fruit. Then you see the animals less and less. They overwinter in the litter.

distribution

The species is widespread across Europe except Scandinavia. In Central Europe, only the black form is found in the north; in the south, the nominate form is mixed with the brown variation salviae .

literature

• Heinz joy , Karl Wilhelm Harde , Gustav Adolf Lohse (ed.): The beetles of Central Europe . tape 11 . Rhynchophora (end). Goecke & Evers, Krefeld 1983, ISBN 3-87263-031-8 .
• G.Jäger (editor): CG Calwer 's Käferbuch . K. Thienemanns, Stuttgart 1876, 3rd edition
• John Curtis: British Entomologie illustrations and descriptions of the genera of insects found in Great Britain and Ireland Volume 7 (Description No. 292) London, Printed for the Author and sold by E. Ellis and Co., 92 Great Russell Street, Bloomsbury, 1823-1840
• Teodosie PERJU and I. MOLDOVAN and Horia BUNESCU: The iris seed weevil-Mononychus punctum-album Hbst. (Curculionidae, Coleoptera) sin Mononychus pseudacori Fb , Notulae Botanicae Horti Agrobotanici Cluj-Napoca vol. 27, No. 1 1997
• Klaus Koch : The Beetles of Central Europe . Ed .: Heinz Freude . tape 3 : ecology . Goecke & Evers, Krefeld 1992, ISBN 3-87263-042-3 . P. 307

Web links

Commons : White-spotted Iris Weevil ( Mononychus punctumalbum )  - Collection of images, videos and audio files

• French website on the biology of Mononychus punctumalbum

Individual evidence

1. ↑ ^{a b c} Fauna Europaea, taxonomy, synonyms and occurrences of Mononychus punctumalbum
2. ↑ Red lists at BioNetworkX
3. ↑ JFW Herbst: Critical directory of my insect collection - archive of insect history 4 and 5: Zurich 1783-84 p. 74. No. 31
4. ↑ Sigmund Schenkling: Explanation of the scientific beetle names (species)
5. ↑ Sigmund Schenkling: Explanation of the scientific beetle names (genus)
6. ↑ Mononychus at Fauna Europaea. Retrieved March 11, 2013
7. ↑ Species of the genus Mononychus at BioLib