Usage and defense of preexisting cavity entrances by the four soldier morphotypes in turtle ants. (A) Photographs of typical entrance sizes and defensive strategies across representative species of the four soldier morphotypes (photos by S.P.). (B) Graphic illustrating typical entrance size and defensive strategy across morphotypes. Square-headed soldiers typically group-block large, often irregularly shaped entrances by haphazardly overlapping their heads like scales; dome-headed soldiers typically group-block moderately large entrances by pushing the domed, posterior region of their heads together and facing the mandibles forward; disc-headed soldiers typically solo-block entrances that only fit a single soldier and mechanically lock the anterior rim of their head disc into the inside surface of the nest entrance; dish-headed soldiers typically solo-block entrances that only fit a single soldier by overlapping the anterior margin of the dish with the entrance hole and pulling back, creating a cap-like seal. For the two group-blocking morphotypes, workers may also participate by wedging their heads into small gaps left around the soldier heads (e.g., smallest individuals in square-headed morphotype photo in A) (30). (C) Graphic illustrating the minimum entrance size and defensive strategy across morphotypes. The minimum entrance size is limited by the size of the soldier’s head in all cases, but only the disc and dish morphotypes typically achieve mechanical locking interactions with the entrance perimeter.