A large specimen of the worker caste of the subtropical ant genus Zacryptocerus is revealed in a clear piece of Dominican amber, making this particular fossil approximately 20-25 MYr (million years) old. Although missing some parts of its legs, this worker is well-preserved and displays a remarkably broad head. An eye and body hairs are even present. Magnification is approx. 10x.

Ancient ants, like those today, were tightly organized social insects that existed in large communities where individuals often displayed distinctive caste-related physical and/or behavioral adaptations. For example, mouthparts and other body structures may possess specialized features, providing clues to the functional role of the individual ant within its society at large. In the case of the ancient ant above note the broad, flattened head, specially adapted to protect the community from invaders by plugging the entrance of the colony dwelling. This adaptation remains in present-day species of Zacryptocerus.