Callosobruchus chinensis

(Linnaeus, 1758)

adzuki bean weevil, pulse beetle, Chinese bruchid, cowpea bruchid

Callosobruchus chinensis is a small in the leaf beetle Chrysomelidae, commonly misidentified as a true weevil due to its . Native to tropical and subtropical Asia, it has spread worldwide through international legume trade. The is a major pest of stored legumes including chickpea, cowpea, lentil, and mungbean, causing significant economic losses. exhibit two distinct morphological forms: -capable forms that emerge later from pods in field conditions, and flightless forms that emerge earlier from dry seeds in storage. The species is frequently confused with the congeneric C. maculatus, with which it exhibits reproductive interference.

Callosobruchus chinensis by Simon Hinkley & Ken Walker, Museum Victoria. Used under a CC BY 3.0 au license.

Pachymerus chinensis by K. Kunhi Kannan. Used under a Public domain license.

Callosobruchus chinensis (Linné, 1758) male by Udo Schmidt. Used under a CC BY-SA 2.0 license.

Pronunciation

How to pronounce Callosobruchus chinensis: /kəˌloʊsoʊˈbrʊkəs tʃaɪˈnɛnsɪs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are approximately 5 mm in length, brown with black and grey patches over the body. Unlike true weevils, C. chinensis lacks a snout. is present: females are larger and heavier than males, with a slightly longer that extends beyond the and is white with two oval black spots. Male are pectinate (narrow and comb-like), while female antennae are serrate (thicker and notched) and shorter. Two morphological forms exist: forms have lighter, larger bodies and larger wings; flightless forms have darker, smaller bodies. Larvae are yellowish-white with reduced legs. Pupae are dark brown and develop inside seeds.

Images

Habitat

Primary is stored legume seeds in granaries, warehouses, and food storage facilities. Field occur on growing legume pods in tropical and subtropical agricultural regions. The shows highest levels during July–August. forms are associated with field conditions on growing pods; flightless forms are associated with dry seed storage conditions.

Distribution

Originally native to tropical and subtropical Asia, with first recorded description from China. Now due to international trade in legumes. Present in stored product facilities worldwide including North America, Oceania, Southern Asia, and Europe (Serbia). Distribution is heavily influenced by human agricultural activity and legume commerce.

Seasonality

Peak production and legume occurs during July–August in field . In storage facilities, breeding continues year-round with multiple possible annually. Total ranges from 29 to 39 days depending on legume and temperature conditions.

Diet

Larvae and feed on legume seeds. Known include chickpea (Cicer arietinum), cowpea, lentil, green gram (mungbean), pigeon pea, black gram, and various other pulses. Larvae feed internally on cotyledons after boring into seeds. Adults feed externally on seed surfaces. Development success varies significantly across host .

Host Associations

Cicer arietinum - primary chickpea
Vigna radiata - green gram, mungbean
Vigna unguiculata - cowpea
Lens culinaris - lentil
Cajanus cajan - pigeon pea
Vigna mungo - black gram
Glycine max - soybean

Life Cycle

Females lay singly on seed surfaces, typically one egg per seed though multiple eggs may be laid when resources are scarce. Eggs hatch in 3–6 days. Larvae burrow into seeds and complete four instars over 12–20 days, feeding internally on cotyledons. Fourth instar constructs a pupal chamber within the seed. lasts 7–10 days. emerge through neat circular exit holes bitten in the seed coat 25 days after hatching. Adult longevity ranges from 7–20 days. Total developmental period from egg to adult is 26–33 days on chickpea at room temperature.

Behavior

Females exhibit selective oviposition, preferentially laying on unoccupied seeds and detecting physicochemical stimuli to avoid seeds with existing eggs. When is high, egg size decreases, producing smaller . Adults exhibit death feigning () as anti- ; frequency and duration decrease with increasing temperature and larger body size. Males court females by raising and rubbing against them. Females release from the during calling posture with raised abdomen and lowered . Males possess large genital that anchor during copulation. Strategic ejaculation occurs based on larval rearing and female mating system. Females may be monandrous or polyandrous depending on strain origin (laboratory vs. field).

Ecological Role

Primary pest of stored legumes causing quantitative and qualitative damage to seeds. Larval tunneling reduces seed weight, germination viability, and market value. Serves as for including Anisopteromalus calandrae and Lariophagus distinguendus, which are used in . Exhibits reproductive interference with congeneric C. maculatus, with C. chinensis males being sexually .

Human Relevance

Major economic pest of stored pulse crops worldwide, causing substantial post-harvest losses. reduces seed quality, germination rates, and commercial value. Controlled through chemical , using , and plant (particularly rosemary and garlic oils in nano-). Subject of extensive research in insect , evolutionary , and . Used as model organism for studying life-history evolution, mating systems, and reproductive interference.

Similar Taxa

Callosobruchus maculatusExtremely similar , lifestyle, and ; frequently misidentified. Distinguished by subtle differences in genitalia and elytral pattern; C. chinensis males have less damaging genital . Reproductive interference occurs between .

Misconceptions

Despite including 'adzuki bean weevil' and 'pulse ,' this is not a true weevil ( Curculionidae) but belongs to the leaf beetle family Chrysomelidae, Bruchinae. The absence of a snout distinguishes it from true weevils.