Gaster (insect anatomy)

The gaster is a special part of an ant's body. It comes from a word in Ancient Greek meaning "belly" or "paunch." It is found in insects called hymenopterans, which include bees, wasps, and ants. In ants, the gaster is the big, rounded rear part of their body.

Inside the gaster, ants have a special space that acts like a "social stomach." This lets them carry food and share it with other ants in their colony. The gaster also holds the ant's heart and the rest of their digestive system.

Some ants, like those in the group Formicinae, can use their gaster to spray formic acid as a defense. Certain ants, such as Cataglyphis bicolor and Cataglyphis fortis, can raise their gaster to move faster. And the ant species Cephalotes atratus can even glide through the air by changing the angle of its gaster while falling.

Parasitism

In ants, the gaster can host certain parasites, including tiny worms called nematodes from the families Mermithidae and Tetradonematidae. These parasites have been living inside ants for around 20 to 30 million years. When an ant is infected, the gaster may swell as the parasite grows inside. Some parasites, like Myrmeconema neotropicum, can even change the color of the ant's gaster to bright red.