Weevil
Beetles with long snouts, many are crop pests.
Weevils are a type of beetle in the superfamily Curculionoidea, most famous for their very long snouts. They tend to be small—under 6 mm long—and plant-eaters. Around 97,000 species are known, with the majority falling under the family Curculionidae, also called the true weevils. This group even includes bark beetles, which lack the classic snout but are still a subfamily of Curculionidae. Some other beetles not closely related also get called weevils, like the bean weevils (a leaf beetle subfamily) and the biscuit weevil, which belongs to Ptinidae.
Many weevils are pests because they can damage or kill crops. The grain weevil and maize weevil spoil stored grain, while the boll weevil attacks cotton by laying eggs inside the bolls, where the larvae eat their way out. On the flip side, some weevils are used to biologically control invasive plants.
A weevil’s rostrum—its elongated snout—holds chewing mouthparts, not the piercing kind found on other insects with proboscises. These mouthparts often dig tunnels into grains. In more advanced weevils, the rostrum has a groove where the first antenna segment can be folded. Most weevils can fly, including pests like the rice weevil, but a fair number are flightless, such as those in the genus *Otiorhynchus*, and some can jump. One species, *Austroplatypus incompertus*, is eusocial—a rare trait outside ants, bees, wasps, and termites.
**Description** Weevils are known for their usually long, thin rostrums, which in some species can be as long as the body, though in others it’s quite short. The mouthparts, including mandibles, sit at the tip. The rostrum’s main job is for egg-laying: it bores deep holes into plant tissue, and then the ovipositor slips in to deposit eggs. Antennae are usually attached near the front of the rostrum. The elytra (hard wing covers) are typically dotted with small holes arranged in rows called striae, often about ten per elytron. The aedeagus (penis) is generally cylindrical. Weevil larvae are soft-bodied, with either no legs or only tiny, useless ones, and are usually slightly curved, though some are strongly curved. Their heads are well-armored with strong mandibles and a downward-facing mouth. The larval body has a three-segment thorax and a ten-segment abdomen, with most segments bearing spiracles for breathing.
Quick Facts
- Taxon
- Curculionoidea
Facts from the source article.
Lore & Background
Weevils are characterized by their distinctive elongate rostrums (snouts), which in some taxa reach or exceed body length. The mouthparts, including mandibles, are at the tip of the rostrum, which primarily serves for oviposition—boring deep holes in plant tissues for egg-laying. The antennae are generally attached toward the front of the rostrum. The elytra are punctured with small holes in striae, typically around 10 per elytron. Larvae are soft-bodied, lacking or having vestigial legs, and generally slightly curved, with a well-sclerotized head and downward-facing mouth.
Larval weevils largely live inside plant tissues, feeding on dying, stressed, or diseased plants, though some have specialized lifestyles such as feeding on dung. Weevils feed on all types of plant tissue, mostly targeting flowering plants, though the most primitive living weevils target conifers. Some weevils have adapted to myrmecophily (living alongside ants), predatory, and parasitic lifestyles. One species, Austroplatypus incompertus, exhibits eusociality, rare outside Hymenoptera and Isoptera.
Sexual dimorphism is extreme in some species: Rhopalapion longirostre females have rostrums twice as long as males, a trait linked to egg deposition, not sexual selection. The New Zealand giraffe weevil shows extreme size dimorphism, with males up to 90 mm and females up to 50 mm.
Reader's Guide
Weevils are among the most diverse beetle groups, with approximately 97,000 described species, most belonging to the family Curculionidae. Their economic significance is substantial: many species are pests that damage stored grain (e.g., grain weevil, maize weevil) or crops like cotton (boll weevil). Conversely, some weevils are employed for biological control of invasive plants. Their taxonomy remains in flux, with higher classification divided into primitive weevils (Orthoceri) and true weevils (Gonatoceri), plus a proposed third division (Heteromorphi). Primitive weevils have straight antennae; true weevils have elbowed antennae. The oldest weevil fossils date to the Middle-Late Jurassic boundary, found in Kazakhstan, Mongolia, China, and Australia. The extinct family Obrieniidae, from the Triassic to possibly the Oxfordian, is sometimes considered weevils but its placement is contested. The interfamilial relationships of Curculionoidea are generally well resolved, with families including Anthribidae, Attelabidae, Belidae, Brentidae, Caridae, Cimberididae, Curculionidae, Mesophyletidae, Nemonychidae, and possibly Obrieniidae. Their ecological roles range from plant tissue feeders to specialized lifestyles, and their morphological diversity—especially the rostrum—makes them a key group for studying evolution and adaptation.
Did You Know?
- Approximately 97,000 species of weevils are known.
- The boll weevil (Anthonomus grandis) attacks cotton crops by laying eggs inside cotton bolls.
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