Can the Ghost Ant (Hymenoptera: Formicidae) Select and Separate Food Inside the Body?

Abstract:
This investigation aimed at analyzing the passage of food inside the digestive system of Tapinoma melanocephalum. A water-soluble dye and a lipid-soluble dye were added to 3 different diets as tracers, to be later offered to different laboratory colonies of the ghost-ant. We collected 80 workers which had ingested the diet, and past set periods of time they were dissected under a stereomicroscope. The ingested quantity of tracers was measured in the infrabuccal pocket, postpharyngeal glands, crop and ventriculus of each ant. Using a video camera, we also recorded 120 min. of the trophallaxis process between the members of one colony. Solid food was retained in the infrabuccal pockets; only liquid diets were actually ingested. Water-soluble tracers were found in infrabuccal pockets, crops and ventriculi, while lipid-soluble tracers were found in infrabuccal pockets, postpharyngeal glands and crops. Carbohydrates mixed up with lipids do not reach the midgut. After 30 min., about half of the colony received food, except the larvae. In 50 min., all workers and queens got food inside their crops. Results suggest that workers can control the passage of food through their digestive system. We also think lipids ingested might be stored and metabolized in the postpharyngeal glands.