# Callosobruchus analis

Callosobruchus analis, also known as the "bean weevil", "cowpea weevil" or the "seed weevil" is a species within the family Chrysomelidae (Subfamily: Bruchinae) which are leaf beetles native to tropical Asia and Africa. C. analis has also been described in locations in the Western Hemisphere such as Brazil due to international trade. Commonly mistaken with another species, Callosobruchus maculatus, both are considered a granivore pests on stored legumes. Despite its name is misleading, C. analis not a true weevil.

## Description

Like other insects in the same genus, C. analis does not morphologically have an elongated rostrum which differentiates it from weevil beetles. Due to the overlapping ranges and similarities among species, insects within Callosobruchus are commonly misidentified. At maturity, the C.analis beetles can vary in length between 3-4 millimetres (mm).

## Lifecycle

Legumes encompass the majority of the lifecycle of C. analis either within in legumes in agricultural storages or unharvested, inedible crops. To attract a male, female insects employ two pheromones to initiate reproduction, one attractant pheromone for and one contact pheromone. The attractant pheromone is released to draw in male insects and once in immediate proximity, the contact pheromone is released, causing male genitalia to extrude and initiate copulation. Copulation within C. analis is conspecific, meaning breeding is restricted solely within its own species and reinforced through the chemical makeup of the contact pheromone to enhance mate recognition. In recent studies, strains of C. analis have been found to undergo scramble competition in which two adults emerge from a single bean. A female, after having undergone copulation, will lay as many as 100 - 200 eggs on suitable legumes. Once hatched, the larvae impregnate themselves into the host bean and internally feed until maturity. C. analis, compared to other insect counterparts such as C. maculatus, displays a 'contest' competition method in which only one single adult insect will emerge from a single bean.
It has been researched that the rearing of larvae and phenotypic traits have been linked to the quality of the hosted bean, to which different bean or seed species have been preferred by C. analis. Lentils have been linked to producing larger offspring while also producing more female-biased insects. Oppositely for mung beans, exhibiting a male bias during larval growth.

## Distribution

Callosobruchus beetles have been described in every continent of the global, primarily seen within the Old World and Eurasian regions. With C. analis is native to equatorial tropics and sub-saharan regions of Africa and Asia, it is most apparent in countries which host high agricultural yield in stored, edible legumes such as India, Ghana and Indonesia. Due to international and intercontinental trade, the insect has experienced expanded ranges to nearly every continent in the world in regions such as Brazil where parasitoids of C.analis eggs have been discovered as well.

## Pest control

Stored foods such as the common bean, cowpea beans and other legumes contribute significantly to international agricultural trade by amount to 27% and comprises 33% of human dietary need. While insects of Callosobruchus directly render legumes unviable through feeding or hosts for reproduction, the majority of legumes are also deemed inedible due to contamination of insect waste products and dead insects, which has been reported to cause 100% loss of product. Notably, countries with emphasis on storing legumes such as Ghana have seen large infestations due to the warmer climate and abundance of legumes in storage.
Recent efforts to combat mass infestations have been through the use of insect pheromones to disrupt mating patterns or to redirect the insects entirely within food product storages. Attractant pheromones have been employed that lure males out of mass storages and while contact pheromones have been used to instigate a false copulation. But due to efficiency and practical measures, phosphine fumigation remains the most common use of beetle management in storages.