Thomas Jefferson Papers

Notes on the Hessian Fly, [1–15 June 1792]

Notes on the Hessian Fly

[1–15 June 1792]

June 1. Mr. Williams brought several stalks with the Chrysalis of the
Hessian fly in them, most were of the flaxseed colour, one only was pale green.
5. a fly is found1 hatched in the morning. qu. how long at 9. aclock laid eggs.
14. 3. do. hatched
15. 1. do.
  Tipula. <Tipu?>  Bibio.  Hessian fly
L. palpi. 2. Enc palpi. 2. palpi. nulli
  Antennae filiform Antennae moniliformus capil breviores. do.
corpore longiore2

Hessian fly. <ab> between the size of a gnat & musketoe

1. the Head. distinct attached by a thread 3. the Abdomen.
2 antennae <(palpi) long> length of the corcelet, hairy,3 articulated <length of the corcelet>, moniliform <hairy?>, the last article truncated 8. annuli, torus-like. saffron colored, with one <br> reddish brown spot on the bottom, or belly of each, and a brown patch on the back
<sucker (haustellum)>
no antennulae.4
2 eyes.
the penis coming out in the line of the axis of the body directly behind, round, with a round gland bigger than the lower part (like a button) hairy
2. the Trunk 4. the Members.
hairy 6. legs
two balances like the plectrum of the sticcada.
2. wings membranaceous, <transp?>6 <veiny naked, Deltoidal> obtuse slate grey, transparent
<with one7 strong nerve passing thro’ it longitudinally about ¼ from the fore edge>
divided into three compartments by two strong nerves running longitudinally
the ground <specked>, strowed with specks & hair like strokes8
June 15. perhaps a male.
1. Head 3 the Abdomen
proboscis clavatum, club-formed with 2 articles at the end.
2. Antennae. 2. <[…]> approximatae10 long as the <whole animal. articulated> body.11 moniliform. <15 articles> 15 oblong conspicuous12 articles above the eyes.
Antennulae. none.
proboscis soft. short.
2. The Trunk 4. the Members.
6. legs.
2. balances.
2 wings. membraneous, hairy clavatae,13 patulae (patent) striated into three compartments by two longitudinal <striae> veins.14
1. Head. distinct attached by a thread. 3. Abdomen
2. antennae. erect.
2 Trunk 4. Members.

MSS (DLC: TJ Papers, 69: 11909, 233: 41666); entirely in TJ’s hand; partially dated; consisting of two loose sheets of slightly different size; printed literally; endorsed by TJ: “Hessian fly.”

TJ wrote these four pages of notes in his capacity of chairman of a committee of the American Philosophical Society investigating the Hessian fly (Mayetiola destructor). This gall midge, thought by many contemporaries to have arrived in America in the straw of Hessian soldiers, was causing serious damage to American wheat crops (see Editorial Note on the northern journey of Jefferson and Madison, in Vol. 20: 445–9, 456–62). The committee had sought information about the pest in a circular printed under 17 Apr. 1792, and on the first of June Jonathan Williams brought specimens for TJ’s observation as responses began to trickle in. Two weeks later TJ informed his son-in-law that he was hatching several flies and that his examination of one specimen led him to suspect the Hessian fly was “aboriginal here” (TJ to Thomas Mann Randolph, Jr., 15 June 1792). The notes and anatomical descriptions printed above document TJ’s researches.

The Editors’ ordering of the two sheets is uncertain but plausible. For his anatomical descriptions, TJ divided three of the four pages into quadrants devoted respectively to the fly’s head, trunk, abdomen, and members. He may have written these headings all at once, with the intention of entering detailed descriptions as he examined each specimen, since the description of a third specimen on the verso of the second sheet was never completed. Characteristically, TJ reworked his notes in order to achieve greater descriptive precision, and his cancellations and interlineations have been recorded in the text and notes (see illustration). Although TJ’s opinion that the Hessian fly was indigenous came to prevail during his lifetime, modern research indicates that it originated in Asia (James Mease to TJ, 12 Oct. 1792; Thomas Say, “Some account of the Insect known by the name of Hessian Fly,” Journal of the Academy of Natural Sciences of Philadelphia, i (1817), 45–8; H. F. Barnes, Gall Midges of Economic Importance, Vol. VII: Gall Midges of Cereal Crops [London, 1956], 95–141, esp. 107).

1Word interlined.

2Recto of first sheet ends here.

3Preceding five words interlined.

4Line inserted during revision.

5Word apparently erased.

6Word interlined and then erased.

7Word interlined in place of “a.”

8Verso of first sheet ends here.

9Line inserted during revision.

10TJ first interlined “2. […]” and then canceled the illegible word and inserted “approximatae” above it.

11Word interlined.

12Word interlined.

13Preceding three words interlined. TJ probably interlined “clavatae” first, then inserted “membraneous” and a comma before it, and finally interlined “hairy” between the two words.

14Recto of second sheet ends here.

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