Pachymerini

Pronunciation

How to pronounce Pachymerini: //ˌpækɪməˈraɪnaɪ//

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Summary

Pachymerini is a tribe of bean weevils or seed beetles, within the subfamily Bruchinae of the family Chrysomelidae. They are widely distributed granivores, known for their compact body shape and habit of infesting seeds.

Physical Characteristics

Bean weevils are generally compact and oval in shape, with sizes ranging from 1 to 22 mm. Colors are usually black or brown, often with mottled patterns. Their mandibles may be elongated, but they lack the long snouts characteristic of true weevils. Notable trait includes short elytra that do not quite reach the tip of the abdomen.

Identification Tips

Look for the compact, oval shape and short elytra of the beetles. The small heads are somewhat bent under. The presence of mottled patterns on their body is also a key feature.

Habitat

Bean weevils typically infest various kinds of seeds or beans and are found in habitats where host plants like legumes, Convolvulaceae, Arecaceae, and Malvaceae are present.

Distribution

Bean weevils are found worldwide, with many species present in tropical regions. Some species are native to Great Britain, while others have been introduced to stored products in warehouses and dwellings.

Diet

They are granivores, primarily feeding on seeds of various plants.

Life Cycle

Adults deposit eggs on seeds, and the larvae chew their way into the seed. Upon reaching maturity, larvae cut an exit hole and pupate, returning to the feeding chamber beforehand.

Reproduction

Eggs are deposited on seeds, where larvae develop within the seeds.

Ecosystem Role

They play a significant role in the ecosystem as granivores, influencing plant populations through their seed consumption.

Economic Impact

Several species are considered pests, damaging stored grains and seeds which can affect agriculture and food supply.

Collecting Methods

• Light traps
• Hand collection from host plants
• Sweep nets

Preservation Methods

• Pinning
• Alcohol preservation
• Drying

Evolution

The tribe Pachymerini has been reclassified from being treated as a separate family to now being included in the Chrysomelidae family as part of the Bruchinae subfamily.

Similar Taxa

• Bruchini
• Amblycerini
• Eubaptini

Misconceptions

Due to their granivorous nature, they are often confused with true weevils, but do not possess the long snouts characteristic of true weevils.

Tags

• Pachymerini
• seed beetles
• bean weevils
• Bruchinae