HORNET CUTICLE - A COMPOSITE STRUCTURE COMPRISED OF A SERIES OF DUPLEX LAMELLAE ATTENUATING TOWARD THE INTERIOR OF THE BODY

Our study deals with the ultramicroscopic structure of the yellow pigm ented cuticular stripes on the abdomen of the oriental hornet Vespa or ientalis (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 patt ern of lamellar attenuation is a linear drop to almost asymptotic thic kness with the innermost lamellae at least one order of magnitude less than that of the outermost one and describable by a mathematic equati on. Each lamella is a composite structure consisting of two primary el ements, namely, a skeleton and filling material. The skeleton is compo sed of chitin and comprised of parallel 'plates' which visibly separat e between the lamellae. These 'plates' are interconnected by: (1) perp endicular 'pillars' which are distributed intermittently at more or le ss uniform intervals; and (2) by a layer of chitin shaped like a horiz ontal helix or at times even a double helix whose diameter equals the distance between two successive lamellae. In the space within the skel etal element there is a filling material of variable nature, mostly pr oteinaceous, which dissolves out and vacates the cuticle during its pr ocessing for microscopic observation, leaving behind the skeletal elem ent. Such structure of the cuticle, wherein two different materials co mbine serially into one duplex structure is typical of composite mater ials. This duplex structuring of the lamellae, combined with their gra dual attenuation and compacting towards the interior, lends the cuticl e in the abdominal region the shape of a thin-walled laminated beam en dowed with a wide array of mechanical, thermal, electric, optic, acous tic and probably numerous other properties which render the cuticle ef ficient for multiple purposes. (C) 1998 Elsevier Science Inc. All righ ts reserved.