Caryedon

Schönherr, 1823

pea and bean weevils, groundnut bruchids

Species Guides

Caryedon serratus(Groundnut Bruchid)

Caryedon is a of seed beetles in the Chrysomelidae, Bruchinae, containing approximately 11 described . The genus includes significant agricultural pests, notably C. serratus (groundnut bruchid) and C. gonagra (also called groundnut bruchid), which infest stored legume seeds. Species in this genus are primarily associated with Fabaceae and have been documented across the Old World tropics and subtropics.

Caryedon by (c) Simon Hinkley & Ken Walker, Museum Victoria, some rights reserved (CC BY). Used under a CC-BY license.

Caryedon serratus by (c) Forest & Kim Starr, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Caryedon: /ˈkæriːɪˌdɒn/

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

Identification

Caryedon are small beetles with body lengths around 4–5 mm based on measurements of C. serratus (mean length 4.10 mm, breadth 3.40 mm). in terminal abdominal segments has been documented in C. gonagra, allowing sex determination in adults. The belongs to the tribe Pachymerini within Bruchinae. Species-level identification requires examination of genitalia and other morphological characters; C. serratus and C. gonagra have been frequently confused in literature due to misidentification.

Images

Habitat

Natural include savanna where develop on seeds of wild legumes such as Piliostigma thonningii. Anthropogenic habitats include stored product environments, particularly groundnut storage facilities, where C. serratus and C. gonagra are major pests. Laboratory rearing indicates successful development at 25–35°C and 60–70% relative humidity.

Distribution

Old World tropics and subtropics, including Africa and Asia. C. gonagra is absent from Australasia and has restricted distribution in the New World tropics. GBIF records indicate presence in Colombia (CO), Norway (NO), and Sweden (SE), though these likely represent introduced or stored product records rather than established .

Seasonality

In savanna environments, C. serratus exhibits multivoltine with 2–3 per year: first generation develops on maturing seeds at the beginning of the dry season, followed by additional generations in dry seeds. enter a semi-lethargic state during the rainy season rather than undergoing pupal . Under constant laboratory conditions, development continues year-round.

Diet

Specialized seed of Fabaceae (Leguminosae). Documented include: Tamarindus indica (principal host for C. gonagra, with faster development than on groundnuts), Arachis hypogaea (groundnut), Piliostigma thonningii (Caesalpinioideae, host for C. serratus in Ivory Coast savanna), and Acacia .

Host Associations

Tamarindus indica - principal C. gonagra develops faster in tamarind pods than in groundnuts
Arachis hypogaea - groundnut; major stored product for C. serratus and C. gonagra
Piliostigma thonningii - Caesalpinioideae; wild in Ivory Coast savanna for C. serratus
Acacia - includes plants (C. acaciae named for this association)

Life Cycle

Complete with , larval (), pupal, and stages. Development rates vary with temperature and humidity. For C. serratus on groundnut: egg incubation 3–6.5 days; larval period 14–33 days; pupal period 13.5 days; adult lifespan 48–76.5 days; total 33–50 days under optimal conditions (30–35°C, 60–70% RH). C. gonagra: 42 days at 30°C and 70% RH; 91–98 days at 25°C. Adults emerge 6 weeks after egg-laying, peaking 1–3 weeks later. Most eggs laid in first 11 days of adult life.

Behavior

females oviposit on seeds, with higher production on unshelled nuts (nearly twice the yield of shelled nuts). Adults of C. serratus enter semi-lethargic state during rainy season as an alternative to . Larvae are the damaging stage, feeding internally within seeds. Sexes distinguishable in adults by terminal abdominal segment differences in at least some .

Ecological Role

Seed specializing on Fabaceae, reducing seed viability and recruitment of plants. Serves as host for complexes including chalcid wasps: documented parasitoids of C. serratus include Uscana caryedoni (oophagous), Anisopteromalus caryedophagus, Bracon sp., Proconura serratocida, and Eurytoma caryedocida (larvo-nymphal).

Human Relevance

Major pest of stored groundnuts (peanuts) in tropical and subtropical regions, causing significant post-harvest losses. C. serratus and C. gonagra are both commonly referred to as "groundnut bruchid" and have been subject to confusion in the literature. Management recommendations include maintaining storage temperatures below 30°C and relative humidity below 60–65% to reduce growth.

Similar Taxa

Other Bruchinae genera (e.g., Acanthoscelides, Bruchus, Callosobruchus)Similar and seed-feeding ; Caryedon distinguished by tribal placement in Pachymerini and association with particular plant groups
Caryedon gonagra vs. C. serratusFrequently confused due to misidentification and shared "groundnut bruchid"; require careful morphological examination for separation, with C. gonagra having faster development on tamarind and broader Old World distribution

Misconceptions

The name "groundnut bruchid" has been applied to both C. serratus and C. gonagra, leading to taxonomic confusion in the literature. Historical records under various names have been consolidated to represent C. gonagra following examination by B.J. Southgate. The attacking groundnuts was previously misidentified, contributing to fragmented and misleading distribution and records.

More Details

Taxonomic note

The Caryedon was historically placed in Bruchidae, which is now treated as Bruchinae within Chrysomelidae. Catalogue of Life classification places Caryedon in subtribe Caryedontina, tribe Pachymerini.

Developmental plasticity

Developmental rates vary substantially with environmental conditions. For C. serratus, duration ranges from 14–18 days at 35°C/65% RH to 33–40 days at 30°C/60% RH, demonstrating significant thermal sensitivity.