1 - Sexual brood and adults were taken from laboratory colonies ofAcromyrmex octospinosus (Reich) for observation and analysis. 2 - The reproductive castes were much larger than the workers. 3 - A sex difference in lipid metabolism was found between the reproductive castes, adult gynes possessing seven times the amount of lipid found in males. 4 - Starved adult males lived for an average of 5.3 days, but gynes survived for up to 109 days (average = 55.4 days). 5 - During starvation, adult males used nearly all of their lipid and carbohydrate reserves, while gynes utilised only neutral lipids to any extent. 6 - The behaviour of gynes appeared to be adapted to the conservation of energy.