Positive allometry in the forceps of the female earwig Anisolabis maritima (Dermaptera: Anisolabididae)

Abstract

Positive allometry and asymmetry in male weaponry have gained widespread recognition in the study of sexual selection. However, few studies have considered these traits in females and there is a significant paucity of data in this field. In this study, we conducted morphological and allometric analyses of the forceps of male and female maritime earwigs (Anisolabis maritima). We conducted a principal component analysis of forceps shape and asymmetry and analysed the allometry of the length and width of the head, thorax, abdomen, and forceps. The results showed that variations in forceps shape accounted for 85% of all morphological variations, whereas variations in forceps asymmetry accounted for only 3%. Male forceps were thick and short, whereas female forceps were thin and long. Positive allometry was observed for male forceps width and female forceps length. Our results indicate that sexual selection may occur in both male and female earwig weapon traits. By examining the allometry of weapon traits in females as well as males, our study contributes to understanding how sexual selection leads to the evolution of weapon traits.