Male and female genital allometry in Habrobracon hebetor (Hymenoptera: Braconidae)

This is particularly apparent within the insects that show high variations in genitalic form between closely related species. Static allometry is one of the effective approaches for quantification of such variation. Despite the crucial roles of the parasitic Hymenoptera in the ecosystems, little is known about the sexual selection in this order, compared with other insect orders. We examined the allometry of different morphological traits in 35 males and 35 females of Habrobracon hebetor (Say, 1836) (Hymenoptera: Braconidae) from a laboratory colony reared in Mashhad city, for the first time. The aim was the investigation of allometric relationships of different body traits as a way for quantification of the natural selection impacts on the different body parts. 12 genitalic and non-genitalic body parts of H. hebetor males and females were photographed and measured. Principal Component Analysis (PCA) was used to explore the variance of the traits and two regression analysis methods to obtain the allometric slopes. All the non-genitalic traits in male and female wasps showed isometry except pterostigma width in male wasps which showed positive allometry. In male genitalia, two traits showed strong negative allometry and one trait showed isometry. Our findings showed that in this species males with an average size of genitalia were more successful in generating viable offspring than males with relatively smaller or larger genitalia sizes and this is irrespective of the overall body size. Our results showed for the first time that such stabilizing sexual selection might operate on genital size in the braconid wasps.