Diacinto (or Giacinto) Cestoni (May 13, 1637 – January 29, 1718) was an Italian naturalist, biologist, botanist, entomologist.

When Cestoni was 11, he left school and entered in the service of a local apothecary where he spent two years as an apprentice, preparing and selling medicines.

[1] Cestoni's time with the local apothecary in Montegiorgio piqued his interest towards natural sciences and in 1650 his family sent him to Rome, where he worked under Roman pharmacist Francesco Boncori.

In 1656, Cestoni moved to the port city of Livorno where he started working in Francesco Salomoni's apothecary shop.

After working in Salomoni's shop for a brief time period, Cestoni left Livorno and would spend the next several years traveling through different cities including Marseille and Lyon to Geneva, practicing and conducting research.

After Redi's death, Cestoni began to write letters to Antonio Vallisnieri discussing his scientific observations.

Vallisnieri published part of Cestoni's observations, inserting them into his own works or into journals such 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 wrote about its effectiveness in powdered form and the dosage and methodology of consuming the drug.

Cestoni examined the sarsaparilla, a plant whose roots are used to make medicine, also historically used in treating syphilis.

In his letters, Cestoni indicates that he did not consider chocolate a medicine, but a tasty food that's hard to digest and therefore whoever consumes it in small quantities will be healthy.

who stated in 1723 that Cestoni had asserted that the coral was nothing but "an insect similar to a small sea oyster or octopus."

In some of his letters addressed to Redi, Cestoni discussed with his friend about stones in the stomach of birds and grafts.

Cestoni and Bonomo described the life history of the itch mite, Sarcoptes Scabiei that causes scabies.

He studied eels, "vinegar eels", "worms" and caterpillars, barnacles, cockroaches, ship mists (lamellibranch mollusc known today as teredine), ants, earthworms, praying mantis, millipedes (myriapods), flies, oysters, fish, lice, bat, green lizard, frog, sea urchin, swallows, toads, salamander, scarab, scolopendra, "flying beetle", "water scorpion", sponges, woodworms, turtle, tapeworms, tarantulas, wasps, vipers, mosquito, ticks, zoophytes.

Through systematic direct observations he had managed to draw a precise picture of the animal's habits.