Weevils (Curculionidae)
MORPHOLOGY AND GENERAL CHARACTERISTICS
Weevils (Curculionidae) constitute one of the most speciose families of Coleoptera, with over 60,000 described species worldwide, making them one of the most abundant groups of terrestrial arthropods. They are particularly diverse in tropical and subtropical regions, but occur in virtually all biomes from boreal forests to semi-arid steppes. The defining morphological trait of weevils is the elongate head forming a rostrum (from Latin rostrum, “beak”), at the apex of which mandibulate mouthparts are located, specialized for boring into plant tissues. This rostrum enables precise oviposition and feeding, and its morphology varies among taxa according to host specialization. Weevils occupy nearly all terrestrial habitats where their host plants occur and exhibit remarkable ecological and evolutionary diversification. Wikipedia
TYPICAL MORPHOLOGY OF WEEVILS
Weevils are generally small to medium-sized (1–40 mm), with robust, sclerotized bodies. Coloration ranges from cryptic browns, greys, and blacks to metallic or patterned integuments, providing camouflage or aposematic signaling. Their exoskeleton often bears microsetae or scales (squamulae), contributing to thermoregulation and defense. Antennae are geniculate and inserted on the rostrum, facilitating mechanoreception and olfaction for host location. Legs are adapted for climbing, with some taxa exhibiting enlarged femora for jumping or substrate adhesion. Sexual dimorphism is frequently expressed in rostral length, antennal morphology, or body size, reflecting reproductive strategies.
GLOBAL DISTRIBUTION AND DIVERSITY
Curculionidae is cosmopolitan, occurring on all continents except Antarctica, with the highest species richness in tropical rainforests. Major lineages radiated in the Cretaceous, in parallel with angiosperm diversification, leading to co-evolutionary specialization. In Europe, approximately 2,000 species are recorded, with over 500 species documented in Central Europe and roughly 300 species reported from the Czech Republic. Globally, weevils occupy a wide range of ecosystems, including tropical lowlands, temperate forests, grasslands, and xeric shrublands. Endemic lineages are notable on islands and in geographically isolated habitats, such as the Hawaiian Trigonoscuta or Madagascan Eurhinus.
FEEDING ECOLOGY
Weevils are predominantly phytophagous (from Greek phyto, “plant” + phagein, “to eat”), feeding on leaves, stems, buds, seeds, fruits, or roots. Many species are highly host-specific, with co-evolutionary adaptations to secondary plant metabolites, whereas others are polyphagous and exploit multiple plant taxa. Certain species, such as the rice weevil (Sitophilus oryzae) and the boll weevil (Anthonomus grandis), are globally significant agricultural pests. Larvae develop endophytically or subterraneously, consuming plant tissue from within, often causing galls, seed loss, or root damage.
LIFE CYCLE AND DEVELOPMENT
Weevils exhibit holometabolous development (complete metamorphosis: egg → larva → pupa → adult). Females oviposit directly into plant tissues or nearby substrate. Larvae are typically legless, creamy-white, and adapted for endophytic feeding, with prolonged larval stages reflecting host tissue quality and environmental conditions. Pupation occurs within plant tissue or soil, and adults emerge fully sclerotized, capable of dispersal. Some species exhibit diapause to survive adverse conditions, with life cycles ranging from several weeks to multiple years in temperate species.
BEHAVIOR AND ECOLOGY
Adults are generally diurnal but may be crepuscular or nocturnal. When threatened, weevils often feign death (thanatosis), retracting their legs and rostrum. Many species engage in host-specific behaviors, including aggregation, mate guarding, and synchronized oviposition. They play a critical role in plant population dynamics, acting as herbivores, pollinators, and vectors for seed dispersal in some ecosystems.
WEEVILS IN THE CZECH REPUBLIC
In the Czech Republic, hundreds of weevil species inhabit forests, meadows, arable land, and gardens. Notable examples include the acorn weevil (Curculio glandium) and the rape seed weevil (Ceutorhynchus napi). Some species are common and readily observable, while others are rare, restricted to specialized habitats such as xerothermic grasslands or old-growth forests.
ECOLOGICAL AND ECONOMIC SIGNIFICANCE
Weevils influence plant community composition and structure through selective herbivory, seed predation, and gall induction. They are prey for birds, amphibians, and predatory insects, and contribute to nutrient cycling. Certain pest species, however, pose substantial economic threats to crops, forest plantations, and stored products, necessitating integrated pest management strategies.
CONSERVATION
Conservation of weevils focuses on habitat preservation, maintenance of host-plant diversity, and mitigation of anthropogenic pressures such as pesticide use and intensive agriculture. Rare and endemic species are protected in nature reserves and under regional or international legislation, with monitoring programs emphasizing species associated with ancient woodlands, xeric habitats, and native plant communities.