All organisms need to communicate with the biotic and abiotic components of their environments. Organisms also communicate within themselves. We saw during our discussions of homeostatic mechanisms and physiological adaptations that insects need to register conditions and changes within themselves and in their environments, and then respond to the conditions. The physiological basis of homeostatic mechanisms is that an organism can somehow measure aspects of the parameters that are regulated. For examples, changes in hemolymph salt concentrations and thoracic temperature need to be registered before corrective action can be initiated.
Insects also respond to changes in their environments.
Mechanisms of entering diapause seem a particularly good example. Here, insects register token stimuli, most often changes in photoperiod. These token stimuli are translated in neuroendocrine events, which in turn are translated into physiological changes. Nervous systems play crucial roles in perceiving environmental conditions, integrating environmental signals into meaningful information, and then producing responses in the forms of internal, physiological events. In another, speedier set of conditions, try imagining how an insect would fly if it could not see where it was going, or could not determine orientation with respect to its horizon.