Weevils

Weevils
Acorn drill ( Curculio glandium )
Systematics
Class : Insects (Insecta) Order : Beetle (Coleoptera) Subordination : Polyphaga Partial order : Cucujiformia Superfamily : Curculionoidea Family : Weevils
Scientific name
Curculionidae
Latreille , 1802

The weevils (Curculionidae) are a family of beetles . In the superfamily Curculionoidea a number of closely related families are grouped together, some of which were previously considered subfamilies, e.g. B. the Apioninae (according to another opinion a subfamily of the Brentidae ). Other, traditionally independent families such as the bark beetles are now regarded as subfamilies. Usually the entire superfamily is understood by the German term weevil .

Weevils are represented worldwide with 40,000 to 60,000 species; an overview from 2007 names 62,000 species. Approx. 1200 species have been found in Central Europe, around 950 of them in Germany. Assuming around 400,000 described beetle species worldwide, weevils make up around 15% of them. Of the (very roughly estimated) two million animal and plant species described, around 3.2% are weevils. This makes the weevils probably the most species-rich family of all living things.

Some species in this family cause damage to agriculture, including the grain weevil , which was found in ancient Egypt; others are stash pests in the household. Recently, however, some species have also been used successfully for biological weed control. By far the most species, however, lead a hidden life, are a few millimeters long and can only be discovered with careful observation.

Way of life of the weevil

Rhopalapion longirostre when mating

Haunted weevil ( Hypera zoilus )

Beetles and larvae of almost all species are phytophagous , that is, they feed on plants. Within the family there are a number of different specialized species; almost all tissues of almost all plant species are used by weevils. Even such tiny plants like duckweed are of a specialized nature ( Tanysphyrus lemnae infested). Only the families Orchidaceae ( orchids ) and Dipsacacee ( cardaceae ) are free of specialized species in the native flora ; The reasons for this are not known. The legless, made similar larvae usually develop in the plant inside, a few live freely (ektophag) (z. B. species of the tribe Hyperini on leguminous plants ). The adults are mostly free living. The eponymous "trunk" is an extension of the head capsule with chewing and biting mouthparts at the tip; often the feelers are turned on the side of the trunk. The elongation is believed to be helpful in feeding in narrow cavities or holes. In addition to species with a long, thin proboscis (up to many bodies length) there are also species with a very short or almost missing proboscis. The subfamilies with a short proboscis usually live on many plant species ( polyphagous ). Some specialize in wood as a source of food ( xylophagous ), in addition to the bark beetles (Scolytinae) , which used to be regarded as a separate family . B. also the Cryptorhynchinae and Cossoninae. In these groups there are also species that live in dead wood, i.e. do not belong to the phytophages in the narrower sense. Most weevils, however, prefer soft tissues such as leaves or herbaceous species . The larvae of some species are root-eating (rhizophag). Larvae of some species mine in leaves, such as the larva of the beech weevil . Others induce growths ( plant galls ) that they feed on. Some species of the genus Curculio live as parasitoids in the plant galls formed by sawfly . Seed-eating species also occur, e.g. B. other types of Curculio in acorns and hazelnuts . Some adults are flower visitors (pollen eaters).

Usually only one generation is passed through each year. The overwintering often takes place in the imaginal stage . Some species are parthenogenetic (i.e., males no longer exist).

Construction of the weevil

These are small to large beetles (1.3–20 mm), which can be clearly recognized by their rostrum (Latin: “trunk”). This trunk-like extension of the mouth area is different in length in the individual species and can even reach more than the length of the body (e.g. hazelnut borer ( Curculio nucum )).

The antennae are usually kneeled: the first link (= antennae shaft) is greatly elongated, followed by the multi-link antenna whip which is attached at an angle.

There is a very different coloration, whereby there are also monochrome types in addition to colored ones. Often, however, the animals are inconspicuously black or black-brown in color, many species are also green or greenish. In many species, the body is covered with scales , similar to the body of butterflies . Others are hairy or almost bald. Some soil-living species accumulate a crust of soil or detritus particles on the outside (mostly fixed by special hook-shaped or club-shaped hairs) and are then hardly to be discovered.

The legs are strongly developed (for slow walking). Some species, such as the beech peacock , can even jump. The feet have five limbs, but the fourth limb is often only indistinctly visible. The undersides of the feet, especially the enlarged third limb, are densely hairy. They are used to hold on to smooth surfaces. The wings are usually developed, but they can also be absent (e.g. in the large black weevil ).

Economic importance of the weevil

Some species, like the furrowed weevil , the pine weevil ( Hylobius abietis ) or the Common Graurüssler ( Brachyderes incanus ) can cause considerable damage in forests and gardens.

Other species are used to control invasive plants. The 2 mm large species Stenopelmus rufinasus from Florida is used in Africa against the large algae fern ( Azolla fulicoloides ). This fern reproduces rapidly, covering the surface of South African waters with a thick carpet of leaves . As a result, important waterways become impassable, and irrigation pumps and pipes become clogged. The dying plant matter removes oxygen from the water, creating a putrid stench. Grazing cattle mistake the carpet for grass, get caught in it and drown. Initial experiments show that Stenopelmus rufinasus , which feeds monophag on Azolla, can effectively push back the fern.

Systematics

The systematics of the weevils was never handled uniformly and remains one of the major problem areas of systematic entomology to this day . In older works, individual features were mostly used for classification, for example the position of the feeler groove or the formation of a hook on the inner edge of the front rails . On the one hand, this procedure has led to systems that are practical for the determination, on the other hand, these systems do not correspond to the actual relationships, as has always been clear from a large number of exceptions and transitions.

In the meantime there have been several attempts to reconstruct the phylogeny of large groups of weevils. Thomson and Marvaldi are examples among many. The results are sometimes quite different, but some of the relationships now seem to be relatively probable:

• The former subfamilies Otiorhynchinae (short-nosed forms with exposed maxillae , the antennae furrows of which are at least partially visible from above) and Brachyderinae (short-nosed forms with lateral, usually downwardly curved antennae furrows) are merged into a new subfamily Entiminae . Individual genera or tribe are, however, transferred to other subfamilies. However, there is no consensus on which ones.
• The former family of the bark beetle (Scolytidae) is a strongly derived branch of the weevil and is incorporated into it as the subfamily Scolytinae.
• The same applies to the former family of beetles (Platypodidae), which now forms the subfamily Platypodinae.
• The subfamily Curculioninae , which in the past included the tribe Tychiini , Curculionini , Ellescini , Acaltyptini and Anthonomini , must be clearly defined. It most likely includes the former subfamilies Rhynchaeninae, Notarinae, Anoplinae, parts of other groups, and probably also the species-rich Ceutorhynchinae. However, the latter are still separated from other authors. The exact extent of the Curculioninae remains unclear.

Overall, the systematics of the Curculionoidea seems to have stabilized somewhat at family level and above. (See Curculionoidea # systematics !). The monophyly of many tribe of the family is now considered certain. The monophyly of numerous subfamilies is still unexplained.

The following list, which divides the family into 12 subfamilies, follows Oberprieler.

• Brachycerinae
• Conoderinae Schönherr , 1833
• Cossoninae Schönherr , 1825
• Curculioninae
• Cyclominae
• Dryophthorinae
• Entiminae
• Lixinae
• Mesoptiliinae
• Molytinae (including Cryptorhynchinae ) Schönherr , 1823
• Platypodinae - core beetles
• Scolytinae Latreille , 1806 - bark beetle

Individual evidence

1. ^ Rolf G. Oberprieler, Adriana E. Marvaldi & Robert S. Anderson: Weevils, weevils, weevils everywhere . In: Zhang, Z.-Q. & Shear, WA (Eds) (2007) Linnaeus Tercentenary: Progress in Invertebrate Taxonomy. Zootaxa, 1668, 1-766.
2. ↑ RT Thomson: Observations on the morphology and classification of weevils (Coleoptera, Curculionoidea) with a key to major groups. Journal of Natural History, 26: 4, 835-891
3. ↑ AE Marvaldi & al .: Molecular and Morphologica Phyllogenetics of Weevils (Coleoptera, Curculionoidea): Do Niche Shifts Accompany Diversification? Syst. Biol. 51 (5): 761-785, 2002
4. Jump up ↑ AE Marvaldi: Higher leven phylogeny of Curculionidae (Coleoptera: Curculionidae) based mainly on larval characters, with special reference to broad-nosed weevils. Cladistics 13: 285-312
5. ^ S. Shin & al .: Phylogenomic data yield new and robust Insights into the Phylogeny and Evolution of Weevils. Molecular Biology and Evolution, Vol 35, Issue 4; April 2018, 823-836
6. ^ Rolf G. Oberprieler: 3.7 Curculionidae Latreille, 1802. In: Richard AB Leschen & Rolf G. Beutel (ed.): Handbook of Zoology. Arthropoda: Insecta. Coleoptera, Beetles, Vol. 3. Morphology and Systematics (Phytophaga). Walter De Gruyter, Berlin / Boston 2014, pp. 423–649. ISBN 978-3-11-027370-0 .

Web links

Commons : Weevils  - Collection of images, videos, and audio files

• Large picture gallery of Central European weevils
• www.curci.de
• www.curculionidae.de
• www.natur-in-nrw.de