Histological sections ofCamponotus(Colobopsis)sp.‘YG’workers confirm that the paired large sacs extending from thehead through the thorax into the abdomen are hypertrophiedmandibular gland reservoirs. This conclusion follows bothfrom the general anatomical organization, with class-3 secre-tory cells opening in the reservoir (Fig. 1A), and from thecharacteristic appearance of a narrow duct linking the reser-voir to a dorsal slit-like groove at the base of the mandible(Fig. 1B). The two cephalic reservoir sacs continue as twonarrow tubes through the thorax and petiole (Fig. 1C) andupon entering the gaster, widen again to become two volumi-nous, blind-ending sacs that occupy more than half of the gas-ter volume (Fig. 1D). Based on a single good series ofsections, the reservoirs would appear to be equal in length. Inits entire range from head to gaster, the reservoir wall is verythin (0.5–1.5lm) with cells containing flat nuclei. It is linedinternally with a thin cuticle of 0.1–0.3lm thickness(Fig.2E).Nomusclefibreswereobservedinassociationwithany part of the reservoir.Secretory cells are restricted to the cephalic portion only ofthe mandibular gland, where they occur in clusters next to thereservoirs (Fig. 2A,B). They belong to class-3, according tothe standard classification of Noirot and Quennedey (1974);thus, each secretory cell is associated with a duct cell that car-ries the secretion to the reservoir. The ovoid-to-polygonalsecretory cells measure approximately 30·20lmandcon-tain a rounded central nucleus with a diameter of about10lm. The duct cell continues into the secretory cell throughan end apparatus, which is formed by a porous central cuticu-lar ductule surrounded by microvilli. The microvilli canappear in a regular pattern (Fig. 2C) or as considerably dis-torted (Fig. 2D), and both situations can be found in cells ofthesameant.Thecytoplasmcontainsnumerousmitochon-dria and some dark-staining secretory droplets (Fig. 2C