The gaster is the bulbous posterior portion of the metasoma found in hymenopterans of the suborder

Apocrita Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" ( petiole) forme ...

(

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...

s and ants). This begins with abdominal segment III on most ants, but some make a constricted postpetiole out of segment III, in which case the gaster begins with abdominal segment IV. Certain ants in the genus ''

Cataglyphis ''Cataglyphis'' is a genus of ant, desert ants, in the subfamily Formicinae. Its most famous species is ''C. bicolor'', the Sahara Desert ant, which runs on hot sand to find insects that died of heat exhaustion, and can, like other several oth ...

'', specifically '' Cataglyphis bicolor'' and '' Cataglyphis fortis'', have a cubiform petiole that allows them to decrease their

inertia Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law o ...

(and therefore increase their speed) by raising their gaster into an upright position.

References

Insect anatomy {{insect-anatomy-stub de:Gaster