Hornet cuticle—a composite structure comprised of a series of duplex lamellae attenuating toward the interior of the body

Abstract Our study deals with the ultramicroscopic structure of the yellow pigmented cuticular stripes on the abdomen of the oriental hornet Vespa orientalis (Hymenoptera, Vespinae). The abdominal cuticle is composed of numerous (more than 25) lamellae which progressively attenuate as one proceeds from the outside interiorly. On a logarithmic scale the pattern of lamellar attenuation is a linear drop to almost asymptotic thickness with the innermost lamellae at least one order of magnitude less than that of the outermost one and describable by a mathematic equation. Each lamella is a composite structure consisting of two primary elements, namely, a skeleton and filling material. The skeleton is composed of chitin and comprised of parallel ‘plates’ which visibly separate between the lamellae. These ‘plates’ are interconnected by: (1) perpendicular ‘pillars’ which are distributed intermittently at more or less uniform intervals; and (2) by a layer of chitin shaped like a horizontal helix or at times even a double helix whose diameter equals the distance between two successive lamellae. In the space within the skeletal element there is a filling material of variable nature, mostly proteinaceous, which dissolves out and vacates the cuticle during its processing for microscopic observation, leaving behind the skeletal element. Such structure of the cuticle, wherein two different materials combine serially into one duplex structure is typical of composite materials. This duplex structuring of the lamellae, combined with their gradual attenuation and compacting towards the interior, lends the cuticle in the abdominal region the shape of a thin-walled laminated beam endowed with a wide array of mechanical, thermal, electric, optic, acoustic and probably numerous other properties which render the cuticle efficient for multiple purposes.