This paper examines the movement of the materials, ideas and practices that went into the construction of natural-historical observations in Paris and the French provinces – in particular, observations of insects. The paired notions of circulation and locality expose the complex dynamic at play in the production of knowledge about these mundane creatures. I show how the movement of things and people problematizes the notion of a single ‘centre of calculation’, even where a dominant figure like Réaumur was managing collections (...) and producing authoritative texts. Réaumur was indeed managing the flow of observations, letters and specimens from his privileged vantage point in Paris, but he was not the only one doing the processing, and the objects and knowledge flowed in all directions. The paper uses correspondence among eighteenth-century naturalists of various sorts to get at the dynamics of circulation, tracing the movements of insects, bits of text or narrative, drawings, letters, questions, apparatus, books and people. My title refers to the activities of naturalists, who had to follow insects around in order to observe them, and to my own activity in following the insects in their movement through letters, conversations, specimen jars, drawings and texts. My research depends on the accumulation of details about experimental and observational practice, culled from the masses of letters that moved continually around Europe, much as the science of insects depended on the accumulation of details about insects – their physiology, habits, metamorphosis and place in the human economy and the economy of nature. (shrink)