Redi’s numerous microscopic inquiries extended knowledge of the intricate complexity of insects. He examined 180 forms of parasites, including ticks, flukes, roundworms and the different varieties of lice compared here. 

In this work, Redi also described a series of controlled experiments investigating the generation of flies.  In opposition to the view that worms and flies generate spontaneously from putrifying meat, Redi showed that only when the decomposing meat was open to the air did life spontaneously appear.  Maggots, or worms, appeared on the rotting meat inside jars that were open to the air, but did not appear inside jars with fine gauze covering the tops that allowed air but not insects to enter.  Redi showed that the maggots appearing on the meat were in fact the larvae of flies, hatched from eggs laid by adult flies.  Female adult flies, Redi observed, contained hundreds of eggs within their bodies.  Instead of spontaneous generation, flies originate from eggs laid by other flies.  All life, Redi reasoned, develops from the seeds of previous organisms of the same kind, as a means of propagating and preserving each species.

After settling in Florence in 1648, Redi served as a physician for the Medici court.  At this time, Ferdinando II de’ Medici, Grand Duke of Tuscany, organized the Academy of Experimentation (Accademia del Cimento), a successor society to the Academy of the Lynx, in which Redi became an active participant (see the Galileo and Experimentation gallery at the NWC).  After Redi’s death in 1697, he was buried in Arezzo, the place of his birth.