Correlation between the head width and larval instars of Sitophilus zeamais (Coleoptera: Curculionidae), and some morphological characteristics of its developmental stages

Abstract

This paper presents the correlation between head width and larval instars of the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) in maize granaries in Son La province. Results showed that there is a strong correlation between head width and age of maize weevil larvae. Head widths varied with the larval instars, being 0.225-0.325 mm, 0.375-0.425 mm, 0.475-0.55 mm, and 0.6-0.775 mm for the first, second, third, and fourth larval instars, respectively. For each instar, changes in head width were accompanied by changes in other characteristics, such as body colour, body width, and body length. This correlation could enable age determination of maize weevil larvae through samples from granaries, allowing detection of the development stage of the maize weevil, Sitophilus zeamais, and prediction of the
appearance of adult weevils inside maize granaries in Son La in particular and Vietnam in general.