Species Callosobruchus maculatus - Cowpea Weevil

Spotted Cowpea Bruchid(1)

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)

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)