Cuticular structures associated with bacterial symbionts of extant and extinct attine ants. (A) Extant A. octospinosus garden-tending ant with Actinobacteria (white) covering the entire body. Image courtesy of Alexander L. Wild (photographer). (B) Actinobacteria growing directly on tubercles (arrows) on the propleural plate of A. octospinosus and (C) A. octospinosus tubercles from which Actinobacteria have been removed, revealing details. (D) Extant T. bugnioni ant with crypts over the entire body. (E) Actinobacteria growing directly on tubercles within crypts (arrows) on the propleural plate of T. bugnioni, and (F) T. bugnioni crypts from which Actinobacteria have been removed, revealing details in which each crypt contains a tubercle. (G) T. primaevus ant fossil embedded in Oligo-Miocene amber from the Dominican Republic, ventral view. (H) Detail of T. primaevus head showing foveae (i.e., pits or crypts). (I) Detail of T. primaevus propleural plate and (J) enlargement, showing dense foveae (arrows indicate pits or crypts). (K) Extant Apterostigma dentigerum, ventral view. Arrows indicate Actinobacteria on mesopleura. (L) A. eowilsoni ant fossil embedded in Oligo-Miocene amber from the Dominican Republic, ventral view. Arrows indicate plumes of bubbles on the mesopleura.