Female accessory reproductive gland activity in the yellow dung fly Scathophaga stercoraria (L.)

The role of the female accessory reproductive glands has been investigated in relatively few insects. Gland secretion has a number of potential functions, including lubrication during copula, involvement in fertilization and protection of eggs. Female yellow dung flies (Scathophaga stercoraria) have large paired accessory glands whose function(s) prior to this study were unknown. Our study indicated glands were involved in copulation and egg laying. The volume of secretion remaining in glands was negatively associated with copulation duration, and this effect was most pronounced in non-ovipositing females. Gland volume and secretion volume remaining in the glands were significantly smaller in females which were allowed to oviposit. In addition, there was a significant interaction between male size, female size and whether or not females were allowed to oviposit which affected the volume of the secretion remaining in the glands, with changes in secretion volume being greatest when males were large. Sperm were found in the accessory glands of some females and this was apparently not related to age, mating history of either sex, to female nutrition or male size. Our results indicate that either large males stimulate greater secretory responses from females or that females alter their responses based on male size.