Thomas Jefferson Papers

To Thomas Jefferson from Ezra L’Hommedieu, 10 September 1791

From Ezra L’Hommedieu

Southold Long Island Sept. 10. 1791.


Since I saw you at this Place I have received from Colo: Sylvester Dering of Shelter Island some Observations he had made on the wheat Insect commonly called the hessian fly, which I send you herewith inclosed with some Stubble of the yellow bearded wheat (as little subject to Injury by the Insect as any we have). By carefully examining this Stubble, by opening the Straw near the Roots and first Joints you will find many of the Insects in their chrysolis State still alive and their Inclosure or Case very Tender. This Stubble was taken from the field in the beginning of Harvest: how long it will be before the Insect comes to perfection if kept in a cool place from the sun is uncertain: but by this Experiment it is easy to see that the Insect might be brought from Germany to New York or carried from us to Europe in the Straw or Stubble but not in the wheat except by much trouble and by design. Yesterday I compared a number of the Insects taken directly from the Stubble in the field with a number that had been taken from Stubble in the same field about a month before and put in a Glass covered with Lawn (in order to observe the Time of the fly coming out) and found them to be in equal forwardness to leave their Chrysalis State. You will find one of the Straws of the Stubble I send tied round with a peice of Twine; just below the Twine you will observe a small hole and at the bottom of the same the Place where the Insect come to Maturity, and being disincumbered from its case and not being able to force its way between the Stalk and Leaf eats through the Leaf. We find many such Straws in our Stubble. The holes I believe were made by the Insect deposited last fall while the leaf was yet tender. How the Insect will extricate itself from its confinement which now remain in the Stubble I shall particularly observe. Altho the yellow bearded wheat and the red bald wheat are not supposed by our Farmers in general to be injured by the Insect yet I make no doubt but the Crop is less by some Bushels in the Acre by the obstruction in the Circulation of the Stalk made by the Insect. If this wheat is sown in poor Land the Stalk will be in proportion feeble and the crop greatly injured. In Guilford this year the same wheat was greatly hurt altho the Land was good owing to the uncommon Number of the Insect there. If wheat was the only vegitable by which these Insects are preserved it would be easy to distroy them by distroying the stubble by burning or otherwise, but I have reason to believe that other vegitables answer for their support but none so well perhaps as wheat.

I have lately received a Letter from Doctor Samuel Mitchell of Queens County (Long Island) who informs me that he is favoured with a Letter from Sir Joseph Banks President of the royal society of London upon the subject of the wheat Insect, who assures him it does not exist in England and he has no reason to beleive its existance in any part of Germany. If the Insect leave the Stubble this fall, it will then be past a Doubt (admitting Colo Derings observations) that the fly is produced in the spring and in the fall, but not three Times in a Year as I supposed to be the case when I saw you and in which he was mistaken. I shall always be happy in giving you every Information I may receive on this Subject or which my own Observations may afford and am with great Esteem & Respect Sir Your most Obedient Servt.,

Ezra L’Hommedieu

RC (DLC); endorsed by TJ as received 22 Oct. 1791 and so recorded in SJL. Enclosure: “Colo. Dering’s Observations on the wheat Insect” (same).

TJ had encountered COLO: Sylvester Dering, whom he described as “particularly serious in his observations on” the hessian fly during his northern tour the previous spring. See Editorial Note and documents on the northern journey of Jefferson and Madison, at 21 May 1791.

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