The role of insulin and octopamine in regulating energy homeostasis and locomotion in insects

Maintaining energy homeostasis is a fundamental requirement for survival. At the core, animals must balance periods of food-searching and feeding with other essential, energy-consuming behaviors. This also applies to insects, which spend a considerable fraction of their lifetime foraging - sometimes under extreme conditions. The motivation to search for food is increased by a lack of energy stores, which drives a hunger signal generated by the interplay between the depletion of energy stores, enteroceptors, and neuroendocrine signaling pathways. These changes alter the internal state of the animal, which modulates the activity of sensorimotor circuits to drive behavioral changes. Here, we review recent insights into the modulation of locomotor activity and foraging by two systems that play critical and antagonistic roles in linking energy homeostasis to behavioral changes in insects and other animals: the insulin and the octopamine system.