Figures of the Article

• Photomicrographs of Gerontoformica sp. in the Myanmar amber specimen STJ-452 Holotype (Individual 1): (a) Frontal view of head features; (b) Frontal view of right antenna; (c) Dorsolateral view ofmesosoma. Paratype (Individual 2): (d) Lateralview of metasoma; (e) Frontal view of head features; (f) Details of left legs’ tarsus and claw.
• Cretaceous worker ants and empty cocoons in the specimen STJ-452：(a) Ventral view of worker individual one (W1) and cocoon one (C1);(b) Lateral view of worker individual two (W2);(c) Photomicrograph of cocoon two (C2) and three (C3);(d) Front end of C3, showing the emergence hole under transmission light; (e) Tail end of C3, showing the meconium under transmission light; (f) Texture of the C2.
• Cretaceous ant pupa in cocoon, preserved in specimen STJ-446：(a)Lateral view of the pupa; (b) Pygidium in detail, showing the sting and the third valvula; (c) Petiole in detail; (d) Texture of the cocoon.
• Strict consensus tree yielded by Traditional Search (Equal-weight) in TNT v. 1.5.Unambiguous morphological character states are shown on the tree with a black circle as the homologous state and a white circle as the homoplasious state.
• Phylogenetic tree of Formicidae, marked with presence and absence of pupal cocoons on the subfamily level.
• Proportions of the genus with documented cocoon existence, showing the relationship between the existence of cocoons and four factors: (a) nesting habits, (b) diet, (c) colony size, and (d) foraging behavior. For data see Table 2.
• Ant cocoons produced by subfamily Haidomyrmecinae found in Myanmar amber (Pictures provided by the amber’s owner).