Acanthoscelides

Pronunciation

How to pronounce Acanthoscelides: /əˌkænθəˈskɛlaɪdiːz/

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Summary

Acanthoscelides obtectus, known as the bean weevil, is a small beetle primarily affecting leguminous crops like beans. It is native to northern South America but has spread worldwide, becoming a significant pest. Adults feed on pollen, while larvae consume seeds, leading to substantial agricultural impacts.

Physical Characteristics

Small beetles, ranging in size from 2 to 5 mm; color from light to dark brown with longitudinal spots on elytra and a red posterior border; yellow-red legs and red-brown antennae; bent head lacking a long snout; eggs are milky white; larvae are white with a yellow head initially and brownish head in later instars, with bristles and three pairs of legs.

Identification Tips

Look for the small size (2 to 5 mm), coloration, and distinctive lack of a long snout. The red posterior border on their elytra and the absence of full elytral cover over the abdomen are also key indicators.

Habitat

Initially native to northern South America, the species is now found globally in warmer climates, particularly where leguminous plants are present.

Distribution

Originally from northern South America, introduced to Europe and now found in Europe, Asia, North and South America, Africa, Australia, and elsewhere. It is common only as far north as northern Lithuania and parts of southwestern Siberia.

Diet

Primarily feeds on the seeds of common beans, peas, vetches, and other leguminous plants; has also been reported on non-legumes like maize and buckwheat.

Life Cycle

Development takes approximately 100 to 110 days, including egg, larval, and pupal stages. Adults hibernate inside seeds or pods, emerge to mate in spring, and can lay up to 200 eggs with typical fecundity around 40.

Reproduction

Females lay 2 to 20 eggs at a time by chewing holes into seed pods, potentially laying up to 200 eggs overall.

Predators

Associated with various parasitoid wasps that target the larvae.

Ecosystem Role

Acts as a pest to legumes, damaging crops in both fields and storage.

Economic Impact

Significant agricultural pest, especially in Australia, with potential crop yield reductions by up to 60%.

Collecting Methods

• Trapping with bait
• Manual collection from infested crops

Preservation Methods

• Drying
• Freezing

Evolution

The genus may be congeneric with Merobruchus.

Similar Taxa

• Merobruchus

Misconceptions

Confusion with the name Bruchus obsoletus due to historical misidentification in the literature.

Tags

• beetles
• pests
• agriculture
• Acanthoscelides obtectus