Spatial memories in insects

whether enough blood circulated in or around the plates to ensure such a function. Furthermore, while the large, flat plates of Stegosaurus might have been thermoregulatory, it is less easy to imagine this working in the spike-like osteoderms of Kentrosaurus. Another possibility is that the plates had a behavioural function, and were used in either sexual selection (there is no apparent sexual dimorphism in plate size, but they may have been different colours in the two sexes), or in species recognition or parent/offspring bonding. Histological differences observed in individuals of different ages also suggest that the plates may have had a communication function — after sexual maturity, the osteoderms grew faster than the skeleton. What did they eat? The small teeth of stegosaurs show they were herbivorous, and the shape of the jaw suggests they may have had a structure that served as a cheek; another possibility is that they had a turtle-like beak. Paradoxically, the teeth of the fossils do not show extreme signs of wear. Furthermore, no gastroliths (stones swallowed by herbivorous dinosaurs and by some birds to aid digestion) have been discovered associated with stegosaur skeletons, so exactly how they processed the vast quantity of food they needed to ingest remains a mystery. The low position of the head in most reconstructions suggest they browsed on low vegetation. However, no coprolites (preserved faeces) have been identified, so more detailed knowledge of their diet is still lacking. The geological context of some fossils suggests they may not have lived close to water sources. How did they move? Stegosaurs are generally thought to have been slow-moving, unable to run for more than a very short distance. However, there is little evidence from trace fossils to confirm this. It has been suggested that they could have reared up on their back legs, using their tail as a tripod. In normal gait, the tail was probably held out horizontally behind the animal, and is thought to have been relatively flexible, reinforcing the assumption that the tail spikes were used as a form of active defence. A number of tail spike fossils show apparent trauma-related damage, and there is circumstantial evidence of a carnivore being wounded by a Stegosaurus tail spike. The tail spikes are now officially known as 'thagomizers', after a Gary Larson cartoon. Were they 'stupid'? Stegosaurs have a reputation for stupidity, which is based on two misconceptions. First, at …