The largest individual in the gestalt colony is the queen (a), almost a meter (3 feet) long and with a bloated body. She lays, on average, one egg per day all year round. Each egg hatches into a juvenile that is cared for by adult worker females that never leave the colony. When the juveniles, both male and female, reach an adolescent stage they work outside the nest. Adult females (b) eventually return to the nest and work as nursemaids. They are prevented from coming into a breeding condition by pheromones (chemical secretions) emitted by the queen. When the queen dies the pheromones stop and a new queen develops from one of the female workers. The female workers and the queen have very small eyes. They find their way about the gloom of the nest's interior by means of sensory protofeathers growing from their shoulders.
The males are soldiers and have poison spines that grow outwards from the headshield (c). They stand guard at the nest entrances, warning of approaching danger by head-banging against the branches (d). Old males may come into breeding condition, shedding their spines (e), adopting a more subdued colour and living inside the nest with the queen. Breeding males are short-lived and are replaced every ten days or so.
The gestalt, Formisaura delacasa, is a small pachycephalosaur with a colonial lifestyle like that of an ant or a termite, from The New Dinosaurs: An Alternative Evolution. It comes from the deciduous and mixed woodlands of Eurasia.
The most remarkable animal of the Palaearctic ecozone must be the gestalt. It is unique among the vertebrates because it pursues a communal existence. The gestalt evolved fairly recently, in the Last Ice Age, when there were few reptiles and non-avian dinosaurs existing in western Eurasia and food was scarce. The animals that did survive there had to develop all kinds of strategies in order to make best use of the food available under the harsh circumstances. The gestalt evolved from one of the smaller pachycephalosaurs (the bone-headed dinosaurs) that lived in herds, mostly in mountainous areas.
The gestalt's strategy was to delegate the breeding of the herd to one individual female, freeing the rest to become food gatherers. They developed the ability to build citadels to guard their hard-won food against other animals. Within this citadel the individuals adhere to a strict discipline and a hierarchy that is based on age and sex. Now that the Last Ice Age has passed, the gestalt has found that its evolved way of life is still very efficient and successful.
Among the pachycephalosaurs the armored head developed as a display structure, particularly in the males. In the gestalt, the male still has a very specialized head, but it is not used for fighting or intimidating members of its own species. The armor has developed spines containing a lethal venom, now used when protecting the colony from predators.
In times of plenty the population tends to grow too big for the colony to sustain. Small groups of adult males and females then leave to start up new colonies. Streams in the temperate regions of Eurasia may be marked by lines of the conical citadels.
The nest is built and kept in repair by the females. It is a thatched structure, built of twigs and straw, usually around a sloping tree trunk over a stream. The interior is a mass of tunnels and chambers and each nest usually has the same layout.
The egg chamber (f) is near the apex where it will be warmed by the sun. The queen chamber (g) is directly below.
The nursery chamber (h), where the hatchlings are tended is below the queen chamber. The toilet area (i) is directly over the stream. The food store (j) is attached to the main trunk and there are up to six additional food stores (k) on other branches of the tree. Long sticks and saplings are woven into the structure to supply escape routes if the main entrance along the tree trunk is rendered impassable by attack or weather damage.
The food of the colony consists of buds in the spring, young shoots in summer and fruits (such as nuts) in the autumn. The adolescents gather the food, passing it along a chain of individuals from one to another until it reaches the nest. This chain is guarded on both sides by adult males.