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Species Callosobruchus maculatus - Cowpea Weevil

Tiny beetle - Callosobruchus maculatus Callosobruchus maculatus Callosobruchus maculatus Tiny brown insect - Callosobruchus maculatus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga
No Taxon (Series Cucujiformia)
Superfamily Chrysomeloidea (Longhorn and Leaf Beetles)
Family Chrysomelidae (Leaf Beetles)
Subfamily Bruchinae (Pea and Bean Weevils)
Tribe Bruchini
Subtribe Acanthoscelidina
Genus Callosobruchus
Species maculatus (Cowpea Weevil)
Other Common Names
Spotted Cowpea Bruchid(1)
Explanation of Names
Callosobruchus maculatus (Fabricius 1775)
2.7–3.0 mm(2)
variable in coloration, leading to confusion with other species of Callosobruchus. Part of the variation is due to the presence of “two distinct adult forms, which differ not only in their morphology, but in physiology, behaviour, etc.” (Utida 1981). Utida (1954) named these “flightless form” and “flight form,” which Caswell (1960) later termed “normal” and “active,” respectively. Utida (1981) discusses at length the basis of the two forms.
adventive, mostly across s. US - Map (2)(3); Cosmopolitan, most likely of African origin
Cowpeas and other beans in storage, incl. Cajanus cajan; Cicer arietinum; Glycine max; Lablab purpureus; Lathyrus spp.; Lens culinaris; Phaseolus spp.; Pisum sativum arvense; Vicia spp.; Vigna spp.(2)
Life Cycle
Do not deposit eggs randomly, but assess their host for its potential to sustain the offspring, generally looking for larger beans and ones with few eggs on them. This increases larval survival by 70%.(4)
One of the best known and most universally destructive of the Bruchidae. Like its sister species, Callosobruchus chinensis, it has the ability to infest and reinfest many species of stored legumes, resulting in enormous post-harvest losses.(2)
However, Callosobruchus maculatus is a non-quarantine/non-actionable species for USDA APHIS. (X. Shirley. pers. comm. to MAQ, 2023)
This beetle deposits a marking pheromone on beans which inhibits egg deposition by its congener C. rhodesianus but the reverse does not occur. When larvae is in competition on beans, C. maculatus larvae will exclude C. rhodesianus larvae.(5)
Works Cited
1.A Dictionary of Entomology
George Gordh, David H. Headrick. 2003. CABI Publishing.
2.Handbook of the Bruchidae of the United States and Canada
Kingsolver J.M. 2004. USDA Tech. Bull. 1912 (2 vols.).
3.Global Biodiversity Information Facility (GBIF)
4.Insect Behavior
Robert W. Matthews and Janice R. Matthews. 1988. Robert E. Krieger Publishing Co.
5.Insect Ecology: Behavior, Populations and Communities
P. W. Price, R. F. Denno, M. D. Eubanks. 2011. Cambridge University Press.