42 



Hessian Fly. 



Vol. II. 



From the Papers of the Pliiladelphia Agricultural Soc. 



IIeis§iau Fly. 



Sharon, Bucks' county, Pa. Feb. 1, I82G. 



Dear Sir, — Among the valuable memoirs 

 of your society, there are several communi- 

 cations relative to the Hessian fiy; but none 

 of them sufficiently traces its history, or offers 

 any plan that can be relied on to prevent its 

 ravages. Indeed, it is lamentable, that an 

 insect of its grade could have been suffered 

 so long to have committed such devastation 

 as has been ascribed to it. 1, iiovvever, trust 

 that its career will soon be closed, having 

 during the last fall had an opportunity of in- 

 vestigating the subject, much to my own 

 satisfaction ; and as the society appears to feel 

 a deep interest in it, I will now give you my 

 ideas upon it. 



On the 9th of October last, my very intel 

 ligent and worthy neighbor, Mr. John Linton 

 informed me, that on the preceding day, he 

 saw the fly in the act of depositing its eggs 

 upon the leaf of the young wheat in the stub- 

 ble-field. Taking this valuable and well- 

 timed hint, on the 11th, I went into the stub- 

 ble field, to witness the interesting spectacle 

 stated by Mr. Linton. I was, however, to- 

 tally disappointed ; not a fly was to be seen ; 

 but on examining the plants with a glass, I 

 found the work was completed; an astonish- 

 ing number of eggs were deposited, scarcely 

 a plant had escaped, and some had more than 

 twenty eggs each. Next day I met with 

 one of the young caterpillars, that had just 

 bursted its shell, and was moving down the 

 leaf: the day r.fter I discovered a plant 

 where the caterpillars had all left the leaf 

 (which I could readily determine by the mark 

 or crust of the egg,) and by carefully strip- 

 ping down the leaf, I saw them on the stalk, 

 about a dozen in number, and some of them 

 within an inch of the root. On the 18th of 

 the same month, the caterpillars had gene- 

 rally passed from the leaf, and many of them 

 had reached tiie end of their journey. About 

 the middle of November, in a warm exposure, 

 some of them had changed to the flaxseed or 

 chrysalis state ; and at this time the most of 

 them are in that state. During my researches, 

 I found them much the most numerous in 

 stubble fields that had not been pastured, and 

 that grain sown after September, had sus- 

 tained no damage. 



The history of the insect and its larvse, as 

 far as I have ascertained by actual observa- 

 tion, is as follows: — The fly certainly depo- 

 sits its eggs in the gutters or furrows of the 

 leaf, on the upper side, from half an inch to 

 an inch or more from the stalk, choosing a 

 position sufficiently exposed to the sun, and 

 affording a sure passage to the stalk, prefer- 



ring plants having only two leaves fully out ; 

 in a few days, probably not exceeding ten, if 

 the weather should be favorable, the eggs 

 (which are oblong, of a brown or somewhat 

 yellow color,) become hatched, and the young 

 caterpillar, of a reddish color, moves down 

 the leaf to its junction with the stalk, then 

 passes between the footstalk of the leaf and 

 body of the plant to near the root, where it is 

 usually seen ; it soon afterwards assumes a 

 transparent white appearance, being probably 

 bleached by its covering; (I infer this, be- 

 cause I met with two cases where there was an 

 aperture at its lodgment — it was nearly black) 

 it there feeds on the sap of the plant, until it 

 attains its full growth, and passes into the 

 chrysalis state ; it seems only calculated to 

 perform a passage from the leaf to near the 

 root ; an outer coat or tegument is there 

 formed, which renders it incapable of further 

 motion ; it then appears perfectly at rest, and 

 is mistaken for an egg or nit (its prior state 

 not having been noticed,) and the injury sus- 

 tained is supposed to be by its pressure upon 

 the stem of the plant, when, in fact, it is a 

 worm actually feeding on its juices: as soon 

 as it changes to the flaxseed color, by rolling 

 it lightly with the finger, the tegument can 

 be taken ofl^, the worm will then appear with 

 a greenish stripe through it, which is evidently 

 the substance extracted from the plant : nei- 

 ther the egg nor young caterpillar, during its 

 movement, can be distinctly seen without a 

 glass ; which every farmer ought to have, as 

 it would enable him at all times to know the 

 state of this and other insects. I think it pro- 

 bable; that another deposit of eggs will take 

 place early in the spring, and perhaps a third 

 between that and fall ; but this conjecture 

 remains for future investigation. 



It appears to me that this insect can be 

 utterly exterminated, by deferring to sow all 

 grains affected by it until the fall deposit 

 takes place; in which case the eggs will be 

 lain on the young plants in the stubble field ; 

 then immediately afterwards commence pas- 

 turing or burning, which will destroy a large 

 proportion, and any time during the larvae 

 state (about the first of November the last 

 season would have been a good time, but even 

 now would answer,) plough up the stubble 

 fields well, which will finish the remainder, 

 except such as are among the plants about 

 stack yards, which must also be attended to. 

 I have satisfactorily proven the efficacy of 

 this plan, by ploughing a field where myriads 

 were lodged ; but it will probably fail of suc- 

 cess, by not being generally gone into at the 

 proper season, and it will be in vain for a few 

 individuals to make the attempt. Let us then 

 endeavor to ascertain that time of sowing 

 which will be attended with most advantages; 

 the first week in October, 1 have often heard 



