Class: Insects
Size: 0.5 to 170mm
Weight: Variable
Age: Variable
Appearance: Variable
Food: Plants, insects, carrion, faeces
Distribution: Worldwide, 350’000 species in 179 families, 8’000 species in Europe
Original location: Worldwide
Natural enemies: Pathogens (viruses, bacteria), predators
Threatened with extinction: No

• Beetles have very different body types, from very long and slender to short and stocky, from flat to strongly spherical. The body shape represents the adaptation to the way of life of the different species.
• Beetles have mouthparts for biting and chewing. These represent the most primitive forms of mouthparts, where the relationship with the head and legs of crustaceans is still recognisable. Nevertheless, they show a high degree of specialisation in their respective diets.
• Beetles inhabit most of the world’s habitats, and there is almost no organic food source that is not used by certain beetle species. Larvae usually feed quite differently from adult beetles. The feeding profiles of the individual species are also very different. Herbivorous beetles range from polyphagous species that feed on different food sources to monophagous species that only eat certain plants. There are many specialists among them: Wood-eaters (xylophages), scavengers (saprophages) that feed on decaying plant parts or that specialise in processing dead wood. Most herbivores feed on leaves, flowers, seeds, roots or stems of plants.
• The predatory families such as ground beetles (Carabidae) have a wide food spectrum. Besides insects, other arthropods, worms, snails and caterpillars, these beetles also eat vertebrates such as tadpoles or small fish (if present).
• Beetles are so-called holometabolous insects, as they change completely during development. During metamorphosis, the eggs hatch into larvae, which then hatch into beetles, which differ greatly from the larvae in appearance and anatomical structure.
• The great diversity of beetles shows that they have adapted to almost all habitats on earth. Apart from the permanent ice of Antarctica and the sea, there is no habitat in which they cannot exist.
• In agriculture, the storage of certain foodstuffs or crops from monocultures provides the best conditions for the reproduction of certain beetle species, which then appear as serious storage pests.
• Beetles find enough food in a very small space. Examples of storage pests, especially in farm shops, are grain and rice beetles, while flour beetle larvae are often found in private households.
• Agricultural pests include Colorado potato beetle, pollen beetle and corn rootworm.
• The American potato beetle and the corn rootworm are good examples of newly emerged species. Their biological invasion was triggered by the importation and cultivation of forage crops in Europe. The imported beetles found a new habitat with good food choices and no natural enemies, which promoted their large-scale spread.
• One beetle whose immigration should be prevented is the Asian hardwood longhorn beetle (Anoplophora glabripennis). These beetles infest many tree species and cause them to die. The species originates from Asia and has now spread to parts of the USA, with a loss of about 150 million US dollars and similar losses in Europe; therefore, this beetle species is classified as a quarantine pest.