Synaptic rearrangement during development characterizes the vertebrate nervous system and was thought to distinguish vertebrates from the invertebrates. However, the examination of the wind-sensitive cercal sensory system of the cricket demonstrated that some identified synaptic connections systematically decrease in strength as an animal matures. Other examinations show that increase in strength over the same period. Moreover, a single sensory neuron could increase the strength of its synaptic connection with one interneuron while decreasing the strength of its connection with another interneuron. Thus, rather than being a hallmark of the vertebrate nervous system, synaptic rearrangement probably characterizes the development of many if not all nervous systems.