Scientific Name:         Acanthoscelides obtectus Say 

Common Names:       Bean Weevil

Synonyms

Bruchidius obtectus

Bruchus obtectus

Laria obtectus

Taxonomic Position

Class: Insecta

Order: Coleoptera

Family: Bruchidae

Genus: Acanthoscelides

Species: Acanthoscelides obtectus

Geographical distribution

USA and Canada, Central and South America, Europe and Northern Asia, Mediterranean Basin, Africa, South and South-East Asia, Australasian - Oceanian, Cosmopolitan

Host Range

Pigeon pea, Phaseolus (beans) and stored pulses

Pest Destructive Stage

Primary pest

Eggs –laid or stuck individually onto seed or pod

Larvae – immobile, concealed within seed

Adults – do not feed on commodity, fly readily

Identification Features - 

Adult

• The adult is 3-4.5 mm long.
• The main colours of the body are greys, browns and reddish-brown, without any distinctive patterns.
• The antennae are dark grey except for segments 1-5 and 11, which are reddish.
• The abdomen is reddish; the legs are reddish, except for the ventral half of the hind (and sometimes the middle) femur which is black.
• Each hind femur has, on the inner ventral ridge near the apex, a large tooth followed by two or three smaller, sharp teeth. (Inner ridge of ventral margin of hind femur with 3 or 4 teeth)
• The setae of the prothorax and elytra are mainly yellowish-grey with darker brown patches.
• In male the pygidium is vertical and only partly visible from above; in females it is oblique and fully visible from above.

Life Cycle

The eggs are laid loosely, but are often lodged under cracks in the bean testa. Infestation may begin in the field, where eggs are laid on ripening pods. Although optimum conditions for development are around 30°C and 70% RH, the species is nevertheless capable of surviving at low temperatures and will breed slowly at 18°C.

Detection methods

Samples can be examined with naked eye or under magnifying glass or stereoscopic binocular microscope and by using soft X-ray and seed transparency method hidden infestation can be detected.