Anthonie Heinsius wrote Letter L-163 of 1685-08-31 about Boyle's idea about the origin of cochineal
This letter is known only by reference and excerpts in another letter. The date is New Style, which was ten days ahead of the Old Style date of 21 August 1685 used by Heinsius in London. For his presence in London, see the Remarks to Letter L-160 of 3 August 1685.
In this letter, Anthonie Heinsius wrote from London that Robert Boyle was satisfied with Leeuwenhoek’s observations of cochineal. Heinsius was replying to Letter L-162 of 10 August 1685, in which Leeuwenhoek reported on his investigation of cochineal. He was, however, on the wrong track because he thought that cochineal, a red dye made from insects, came from the seed of a plant. Based on what Boyle relayed to him through Heinsius, Leeuwenhoek recanted his 10 August letter in Letter L-164 of 21 September 1685. Both letters are known only by excerpts in Letter L-194 of 28 November 1687.
Letter 105 [60] L-194 of 28 November 1687 to the Royal Society
To this, the abovementioned Mr. Heinsius replies to me from Westminster on the 21st/31st August.
"I have communicated to Mr. Boyle the contents of the missive which you sent me, about which his honour was very satisfied. He requested me to thank you for the trouble you have taken, etc:
“Your argument concerning the invariably similar little animals in the male seeds, etc:.
“As regards the cochineal, he says that he understood from a governor of Jamaica that the same originates in the fruit of a fig tree, which, on rotting or putrefying, produce worms, or cocoons, which change into flies and these settle and hold themselves on very tight to the tree; a fire is then lit under the tree, and the smoke causes them all to fall down, and after they are caught the head and the foremost part, together with the wings are removed and the rest is kept, so that the cochineal is really the hindmost part or the tail of the fly. And furthermore, he has approved of the observation which You yourself made concerning the matter, and he is of the opinion that what you have seen are, in fact, eggs, just as we find such eggs in the abdomens of the silk-worms’ moths."
