(b. Montegiorgio, Italy, 10 or 13 May 1637; d. Leghorn, Italy, 29 January 1718),
Cestoni was born of poor parents, who did, however, send him to school until 1648. In that year he was apprenticed to a pharmacist, thus embarking on the profession he was to pursue the rest of his life. In 1650 he entered the service of a Roman pharmacist.
He left Rome in 1656 and set out to travel, using his modest savings. So he reached Leghorn, taking up again the practice of his profession. In 1666 he set out again, traveling via Marseilles and Lyons to Geneva, where he practiced pharmacy for about four months. Returning to Leghorn, Cestoni resumed his old job. He married in 1668 and spent the remainder of his life in Leghorn.
The grand ducal court summered in Leghorn, which facilitated his encounters with Francesco Redi, the chief physician to the grand duke. In 1680 Cestoni and Redi began a lively correspondence, which is known chiefly through Redi’s letters.
When Redi died in 1697, Cestoni began to write weekly letters to Antonio Vallisnieri. Most of Cestoni’s observations contained in the correspondence seem to have been made prior to 1697, however. A real friendship developed between the two men, and Vallisnieri visited Cestoni in Leghorn in 1705.
Vallisnieri published only part of Cestoni’s observations, inserting them into his own works or into such journals as the Galleria di Minerva and the Giornale de’ letterati d’Italia Among the few observations published abroad were those on the metamorphic cycle of the flea which appeared in the Philosophical Transactions of the Royal Society.
Cestoni’s principal subject of study was the generation of insects, and in this field Redi and Vallisnieri found him a valuable ally in working to disprove the theory of spontaneous generation. Connected with his studies on the generation of insects was the discovery of the acarid etiology of mange in collaboration with G. C. Bonomo. The latter published their discovery in the form of a letter to Redi, Osservazioni intorno a’ pellicelli del corpo umano (Florence, 1687).
The Cestoni-Vallisnieri correspondence (for the most part published in 1940) merits systematic critical analysis in order to assign each of Cestoni’s numerous observations its precise place in the general development of science. His observations on the parthenogenesis and the viviparity of the aphides seem especially relevant.
The major source of information on Cestoni is Epistolario ad Antonio Vallisnieri, 2 vols, (Rome, 1940–1941).
An extract of a letter written by Cestoni to Martin Lister (24 Nov. 1698), concerning Redi’s manuscripts and the generation of fleas, was published as “A New Discovery of the Origin of Fleas, Made by Signior D’iacinto Cestoni of Leghorn,” in Philosophical Transactions of the Royal Society. 21 (1699), 42–43.