Frederik Adriaan van Reede van Renswoude

Baron van Reede van Renswoude, from Utrecht, was a diplomat, peace negotiator, and member of the States General. He was married to Maria Duyst van Voorhout, from one of Delft's oldest and wealthiest regent families and probably a longtime friend of Leeuwenhoek.

The Baron van Reede was interested in scientific subjects and often visited with Leeuwenhoek, who addressed twelve letters to him between April 1695 and August 1701.

During his marriage, van Reede lived in den Haag. He was also noted for his arrest for sodomy when he was in his 70's. See: Utrecht sodomy trials

Van Reede seems to have initiated an exchange of letters by sending L. a caterpillar to study some time before Leeuwenhoek sent his first letter to Van Reede, Letter L-248 of 22 April 1695. Van Reede replied to that letter with the present letter before L.’s next Letter L-253 of 18 May 1695, to which Van Reede replied with Letter L-257 of June 1695.

Over the following year, Leeuwenhoek wrote six more letters to Van Reede without receiving a reply, mostly about problems with the 30-tree apple orchard in his own garden outside Delft’s Waterslootse Poort. Perhaps Van Reede was having similar problems with the orchard at his estate, Renswoude, and its garden pests: the apple-blossom weevil, black flies, caterpillars, and ermine moths. Leeuwenhoek also wrote about the anatomy, especially the sexual organs, of aphids, lice, and oysters. Leeuwenhoek published all of these letters in Vijfde and Sesde Vervolg der Brieven. These letters also include Letter L-281 of December 1695, the dedication to Vijfde Vervolg der Brieven, geschreven aan verscheide Hoge Standspersonen ed Geleerde Luijden (Fifth continuation of the letters, written to various high-standing persons and learned people).

In that dedication, Leeuwenhoek notes his frequent visits to Renswoude, Van Reede’s estate between Amersfoort and Arnhem, far enough away that he would have to spend the night. He visited along with his unmarried adult daughter Maria, who grew up across the Hippolytusbuurt gracht from Maria Duyst van Voorhout (1662-1754), the wife of Van Reede. These visits might explain why only three letters are known from Van Reede to Leeuwenhoek, the present Letter L-249 of early May 1695, Letter L-257 of June 1695, and Letter L-299 of 23 August 1696.

Following Van Reede’s Letter L-299 of 23 August 1696, Leeuwenhoek wrote six more letters to Van Reede, without a known reply. Leeuwenhoek’s letters were about, among other things, plant-lice, black flies, caterpillars, willow-wood, peat, and measuring the fall of water. He also wrote about oysters, shrimp, ling, haddock, roach, and cod, and how scales determine the age of various fish.