Summary — The cornual gland of the drone's endophallus is an epithelial gland, whose cells extend from the tip of the cornual tube, along its lateral parts to the basic hump (dorsal cornua). The gland forms a stripe with a central region of dense and homogeneous secretory cells. To the sides the gland cells become sparse. The secretory cells contain mainly rough endoplasmatic reticulum and numerous mitochondria. The nuclei have several nucleoli and are situated at the apical part. Microvilli border the microfibrillar cuticula into which cell projections often intrude. At the basal membrane the cells are often subtended by a layer of fatty tissue, and oenocytes can also be attached. The secretion in a 3-day-old drone appears either as an orange-coloured layer (deep frozen sections) or as osmiophilic granula (EM) mainly near the lumen of the cornual tube. The cuticula of the cornual tube is untanned and non-sclerotized. Along the lumen of the cornua it is extremely folded and papillated, forming in situ small cavities which contain osmiophilic drops of the secretion, often accumulated in groups. No pores were found, although small granules of secretion occur within the cuticular layers, with the highest concentration near the lumen. During eversion of the cornua the secretion merges on the surface of the cuticula. The cuticula consists of two differently structured layers. Near the lumen of the cornual tube the microfibers extend regular and parallel to the folds; above the gland cells the microfibers are less dense and more irregular.Apis mellifera / drone / sexual organ / endophallus / cornual gland INTRODUCTION

Summary — The orange cornual layer of the drone's endophallus is produced by gland cells in the epithelium of the comua. The occurrence of its pigment is age-dependent as newly emerged drones have no pigmentation, and all colony drones older than 4 d had orange comua during the reproductive season (May and June). The absorbancy spectrum of the pigments extracted in dioxane has maxima at 300 nm, 380 nm and 500 nm. In extracts from 4-d-old drones, the amount of absorbing substances was less than in extracts from 12-d-old drones, although all types of pigments were present. The production of the pigments is related to seasonal fluctuation.