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Acanthoscelides obtectus Say
Acanthoscelides obsoletus Say

Insecta, Coleoptera, Bruchidae .

Bean bruchid

Description, Biology, Life Cycle, Damage, Common Names, Images

- Adult: 3.2 to 4.0 mm. Conical prothorax, posterior femora bearing a strong notched tooth. Reddish legs, orangy red abdomen and pygidium. Reddish brown or greenish grey pronotum and elytra except the posterior border which is reddish (*) .
- Eggs: milky white; 0.60 mm x 0.25 mm.
- Larva: first-instar larva with a yellow head and long legs. Arched second-instar larva, apodous, white with a brownish head.

- This beetle develops mainly on bean, more rarely on soja and lentil.
- Adult: hibernates inside the seeds, each being able to contain several individuals. It starts to move around in the seed storehouses or in the fields once the temperature reaches 11 °C, and flies in dry and sunny weather (21°C). Lifespan of hibernating adults: 3 to 4 months. The eggs are deposited in clusters of 2 to 20 on the pods or inside them, on the innerside or directly on the seeds. Average fecundity: 40 eggs.
- Eggs: short embryonic development of 3 to 15 days.
- Larva: the 1st-instar larva moves about on the pods, then enters one of them; after 2 to 3 days, it digs into the seed then moults, and transforms into the 2nd-instar larva. By the end of its growth which lasts about 3 weeks, it cuts an exit operculum in the side of the seed and then pupates.
- Pupa: development lasts 12 to 25 days.

[R]Life Cycle
- This beetle belongs to the group of multivoltine bruchids so that if the seeds are stored in a particularly warm place, 2 to 3 generations can follow one another during the year, in addition to the summer generation which occurs in the field, at least in the southern half of France.
- The adults having hibernated emerge from the seeds in April, do not feed and mate. The first generation adult appears in mid-July. As early as end of July, laying can begin on stored seeds.

This beetle, which develops at the expense of the seeds, in particular those of bean, is extremely harmful, especially since it can multiply in warehouses (*) .

Originating from America, the bean bruchid slowly invaded the whole of France up till about 1920.
In Spain, this beetle has been known for a long time.

[R]Common Names
DE: Speisebohnenkäfer ES: Gorgojo de la judia FR: Bruche du haricot IT: Tonchio del fagiolo PT: Gorgulho do feijão GB: Bean bruchid, Bean seed beetle, Common bean weevil

[R] Images

  1. Acanthoscelides obtectus (Say) (Coutin R. / OPIE)
    Adult vacating an attacked grain Using its mandibles, the adult has cut a circular hole in tegument.
  2. Acanthoscelides obtectus (Say) (Coutin R. / OPIE)
    Damage on haricot bean
  3. Acanthoscelides obtectus (Say) (Coutin R. / OPIE)
    Adult on an attacked grain

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