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Acanthoscelides obtectus Say
Acanthoscelides obsoletus Say

Insecta, Coleoptera, Bruchidae .

Bean bruchid

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


[R]Description
- 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.

[R]Biology
- 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.

[R]Damage
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 (*) .

[R]Remark/A>
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.
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  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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