Abstract
Honey bees head capsule have a pair of hypopharyngeal glands (HPGs) made of vesicle-like structures called acini. These acini are connected by a large duct running to hypopharynx. Their prime function is to secrete royal jelly and other proteinaceous elements in nurse honey bees. Royal jelly is a proteinaceous food which is fed for the initial three days of the general brood/ (workers and drones) while for the complete larval stage to that brood which is destined for queen development. Changes occur in physiology and morphology of HPGs with the age of honey bees and these phenomena is referred as age polyethism. In this study morphometric variations were determined in acini size of western honey bee (Apis mellifera) and native honey bee (A. cerana) of Pakistan. HPGs in nurse and forager castes of both species were exposed by dissecting the head capsule, isolated, and placed on microscopic slides. The acini mounted on slides were placed under a stereomicroscope and their sizes were measured. A significant difference in acini size between A. mellifera and A. cerana nurses (0.046 and 0.039 mm(2)) was observed during the summer and the winter (0.040 and 0.033 mm(2)). Foragers acini size of A. mellifera and A. cerana were (0.017 and 0.014 mm(2)) in the summer and (0.014 and 0.012 mm(2)) in the winter, respectively. It was observed that A. mellifera has larger acini size as compared to A. cerana. It is concluded that the acini were full-grown in nurses as compared to foragers in both honey bee species. Acini were larger in a summer season as compared to the winter season. No previous study of this kind was performed in Pakistan on (A. cerana)