The female Geometridae are characterized by the presence of saccular pheromone glands. They are paired structures, invaginated anteriorly and located dorso-laterally to the rectum. The opening of dorsal saccular glands varies from wide to narrow and opens up on the 9th abdominal segment. These saccular glands are widely distributed in the family. Morphological variability of these glands can be observed. In certain species of Geometridae, the paired glands vary from short to long. Pheromone production is an established function of these glands, in the case of Rheumaptera hastata.