Callosobruchus

Pronunciation

How to pronounce Callosobruchus: /kəˌloʊsoʊˈbruːkəs/

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Summary

Callosobruchus maculatus, commonly known as the cowpea weevil, is a cosmopolitan pest of stored legumes. It exhibits sexual dimorphism and has two morphs. Its life cycle involves developing within beans and laying eggs in storage or fields. The species is significant in agriculture due to the damage it inflicts on legume crops.

Physical Characteristics

Reddish-brown overall with black and gray elytra marked with two central black spots. The last segment of the abdomen extends out from under the short elytra, and has two black spots. Females are darker than males, with a larger dark plate covering the abdomen. Two morphs exist: a flightless form and a flying form.

Identification Tips

Callosobruchus maculatus lacks the snout characteristic of true weevils and is more elongated than other leaf beetles. Males are generally brown while females are darker and can be larger.

Habitat

Temperature and humidity in legume storage areas are relatively constant, with high food density. Females lay eggs on legumes in the field or in storage.

Distribution

Cosmopolitan; occurs on every continent except Antarctica. Likely originated in West Africa and spread globally through trade.

Diet

Larvae feed on the interior of various legumes, including cowpea (Vigna unguiculata), mung beans (Vigna radiata), and adzuki beans (Vigna angularis).

Life Cycle

Females lay over a hundred eggs on legumes, with larvae hatching 4 to 8 days after. Larvae develop inside the beans, taking 3 to 7 weeks to mature, longer in colder climates. Lifespan is typically 10 to 14 days as adults, but may extend to three to four weeks in colder areas.

Reproduction

Copulation can injure females due to penile spines of males, which may reduce their mating success with other males. Females glue eggs to legumes post-mating.

Predators

Parasitoid wasps such as Anisopteromalus calandrae, Uscana mukerjii, and Dinarmus basalis target C. maculatus.

Ecosystem Role

As a pest, C. maculatus plays a significant role in the dynamics of legume storage and agriculture, often leading to economic loss.

Economic Impact

Considered a damaging agricultural pest, particularly in developing countries where it infests stored legumes.

Health Concerns

Regarded as medically harmless to humans; primarily affects agricultural output.

Evolution

C. maculatus has gone through multiple population bottlenecks due to its spread with human trade, leading to inbreeding despite the persistence of the species.

Similar Taxa

• Callosobruchus chinensis

Misconceptions

Often mistaken for true weevils; it is not a true weevil.

Tags

• beetle
• agricultural pest
• cowpea weevil
• legume pest
• insecta