This study examines the time budgeted to different behaviors in Aplysia fasciata under three conditions: (1) animals have constant access to food and mates: (2) there is access to food, but not to mates; (3) neither food nor mates are present. The data suggest a number of rules underlying behavioral integration: (1) Feeding, reproductive behaviors, and activity seem to be natural categories for behavioral choice. Feeding and reproductive behaviors are controlled in tandem by a common arousal mechanism, while time left over after animals feed and reproduce is distributed in a fixed ratio between locomotion (crawling and swimming) and inactivity (immobility and movement in place). (2) Relative distribution between different forms of locomotion and inactivity is modified by changes in motivational state. More time is spent swimming than crawling when feeding and/or mating is prevented, while more time is spent moving in place than immobile when the arousal level is increased. (3) Feedback control of feeding and reproduction is asymmetric. Satiation of feeding inhibits the common arousal. In the absence of food, time spent on reproductive behaviors increases due to disinhibition of the common arousal. By contrast, positive feedback arising from sexual behavior excites the common arousal. When mating is prevented by removing potential mates, time spent feeding decreases. (4) Generally, animals choose between performing the three main categories of behavior. Although Aplysia simultaneously can feed and mate, or locomote and mate, they do so infrequently. By contrast, different types of reproductive behaviors (male mating, female mating, egg-laying) are commonly performed simultaneously.