Fine structure of the gemma gland in the ant Diacamma australe (Hymenoptera, Formicidae).

Workers of Diacamma have minute mesothoracic appendages termed <<gemmae>>, and these represent a unique glandular structure among the Formicidae. In D. australe, each gemma contains approx. 500 glandular cells which are individually connected by duct cells opening through minute pores on the outer surface of the gemma. A specialized end apparatus forms the junction between the two cell types. Ultrastructural examination of the secretory cells shows the presence of both smooth and granular endoplasmic reticulum, and the occurrence of both electron-lucid and electron-dense inclusions. The secretion may therefore have a rather complex composition. Its function is presumably related to the peculiar mechanism of reproductive regulation found in this queenless ant.