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