  Like a rocket being propelled into space, evolution has engineered flies to
launch into adulthood via multiple stages. Flies develop and deploy two
distinct bodies, linked by the transformative process of metamorphosis. The fly
larva is a soft hydraulic tube that can crawl to find food and avoid predators.
The adult fly has a stiff exoskeleton with articulated limbs capable of
long-distance navigation and rich social interactions. Because the larval and
adult forms are so distinct in structure, they require distinct strategies for
sensing and moving the body. The metamorphic divide thus presents an
opportunity for comparative analysis of neural circuits. Here, we review recent
progress toward understanding the neural mechanisms of proprioception and motor
control in larval and adult Drosophila. We highlight commonalities that point
toward general principles of sensorimotor control and differences that may
reflect unique constraints imposed by biomechanics. Finally, we discuss
emerging opportunities for comparative analysis of neural circuit architecture
in the fly and other animal species.
