Darkling Beetles (Tenebrionidae)
TENEBRIONIDAE – MORPHOLOGY, ECOLOGY, AND GLOBAL DISTRIBUTION
Darkling beetles (Tenebrionidae; from Latin tenebrio “one who loves darkness,” referring to their crepuscular or nocturnal habits) constitute one of the largest beetle families, encompassing over 20,000 described species worldwide. In Europe, approximately 2,000 species are recorded, with roughly 300 species occurring in the Czech Republic. Adult sizes range from 2 to 30 mm. Morphologically, tenebrionids are robust, elongate or ovate, with heavily sclerotized elytra, typically black or brown, often with hygroscopic properties that enable absorption of atmospheric moisture. The head bears short filiform antennae and powerful mandibles adapted to dry diets. Legs are cursorial, facilitating running across soil or climbing substrates. Both adults and larvae are primarily saprophagous, feeding on dry wood, fungi, seeds, or stored products such as flour. Certain genera, such as Blaps, possess defensive glands (anal exudates) for chemical deterrence. Wikipedia
DISTRIBUTION AND SPECIES IN THE CZECH REPUBLIC
In the Czech Republic, common representatives include the yellow mealworm beetle Tenebrio molitor (12–18 mm), a synanthropic pest of flour and cereals; Blaps mucronata (20–25 mm), inhabiting buildings and forest floors; and Opatrum tibiale, which occurs in tree cavities. Tenebrionids are widespread in dry forests, steppes, and synanthropic environments. Globally, they are highly diversified in arid and semi-arid regions, from temperate to tropical zones. They occupy habitats under bark, in bird nests, leaf litter, and human structures. Rare forest-dwelling species are threatened due to habitat alteration and are included on regional Red Lists.
ECOLOGY AND HABITAT PREFERENCES
Darkling beetles inhabit xeric ecosystems such as dry forests, steppes, under bark, in cavities, bird nests, granaries, and compost heaps. Adults consume dry organic debris, fungi, or seeds. They are nocturnal and most active during high humidity, with adaptations to aridity provided by their hygroscopic elytra. Larvae develop in substrate over 6 months to 2 years, contributing to decomposition processes and organic matter recycling in terrestrial ecosystems.
LARVAL BIOLOGY – MEALWORMS
Tenebrionid larvae, commonly known as mealworms in Tenebrio molitor, are yellow-brown, elongate, and reach up to 30 mm in length. They molt 10–15 times over a period of 4–18 months and consume flour, grains, or vegetable matter. Larvae are widely used in aviculture and herpetoculture as high-protein feed. Ecologically, larval feeding accelerates decomposition and nutrient cycling in dry habitats.
REPRODUCTION AND LIFE CYCLE
Females lay 200–500 adhesive eggs into substrate from spring through autumn, hatching within 1–2 weeks. Larval development spans 3–18 months depending on temperature and food availability, after which larvae pupate near the surface. The full life cycle ranges from 6 months to 2 years. Adults live 2–6 months and may produce 1–3 generations annually under warm conditions.
ECOLOGICAL AND ECONOMIC IMPORTANCE
Tenebrionids have dual significance. Larvae are economically valuable as feed for exotic birds, reptiles, and fish, while adults can be pests of stored products. In natural habitats, they play a key role in decomposition and nutrient recycling. Rare forest-dwelling species are threatened by intensive forestry practices and benefit from the retention of cavity-bearing trees, dead wood, and systematic monitoring. Conservation strategies include the preservation of dry habitats, maintenance of natural organic substrates, and biological control in synanthropic settings.
Project for Czech children “Little Naturalist”
GLOBAL CONTEXT
Tenebrionidae exhibit cosmopolitan distribution but reach their greatest species richness in arid and semi-arid environments, including deserts, dry tropical forests, and Mediterranean woodlands. Their evolutionary success is attributed to adaptations to xeric conditions, including hygroscopic cuticle properties, nocturnal or crepuscular activity, and versatile feeding habits ranging from saprophagy to granivory. These adaptations allow tenebrionids to colonize a wide range of terrestrial habitats across all biogeographic realms, making them a key component of dry ecosystem food webs and nutrient cycles. Beetle