Distribution and Comparative Morphology of the Cloacal Gland in Ants (hymenoptera: Formicidae)

The cloacal gland is a paired exocrine structure, which has so far been described only in the formicine species, Camponotus ephippium and Cataglyphis savignyi (Hymenoptera : Formicidae). The gland is formed by 2 clusters of bicellular units with slender duct cells, releasing the glandular secretion through the cloacal membrane. In the present work, a number of ant species, largely of the Formicinae subfamily, have been surveyed for the presence of a cloacal gland. The gland is be present in nearly all formicines screened, albeit with a variable development. Cataglyphis, as one of the genera with a very prominent cloacal gland, was chosen for a more detailed comparative study. At the ultrastructural level, secretory cells were observed having a welldeveloped smooth endoplasmic reticulum and Golgi apparatus, typical for pheromone-producing glandular cells. The gland is also present in all dolichoderines screened, but in none of the species of the Aneuretinae, Myrmeciinae, Myrmicinae, Nothomyrmeciinae, or Pseudomyrmecinae investigated. This provides a tentative evidence that the cloacal gland is a synapomorphy of the Formicinae and Dolichoderinae, giving support for their hypothesised sister group relationship. Up to now, the function of the cloacal gland remains largely enigmatic.  1998 Elsevier Science Ltd. All rights reserved. Index descriptors (in addition to those in title): ultrastructure; exocrine glands; sternal glands; phylogeny; scanning electron microscopy.