AND H O R T I (; U L T U R A L R K (i I S r 10 R . 



rUULISHEO BY JOSKPU UllEClC vV CO., NO. (H NOliTH M.VllKKT STllliKT, (Aohicultuiial Wa«chou.«.)-ALLEN PUTNAM, KDITOR. 



BOSTON, WEDNKSDAY EVKNING, JUI-Y 21, 1841. 



CHO. 3. 



N. E . FARMER. 



From Silliman't American Journil of Sciance. 

 MIE HKSSIAN FLY AND ITS PARASITES. 



BT KDIVaRP C. lltllRICK. 



%For several yours paat I liavc spent soiiio time 

 n tlie study of the habits of the Hessian fly, nnii 

 if the various insects by which it is attacked. Du- 

 ing a part of the period I enjoyed the important 

 o-oporalion of my valued friend, Mr James D. Da- 

 la, ni>iv abs'nt from the country, as one of the 

 cientitic corps of the United Stales South Sea 

 Jxplorini; Expedition. It was, and still continues 

 o be, my intention to offer an extended paper on 

 his subject. The investigation is not yet in every 

 (articular so complete as could be wished, but se- 

 'eral circumstances seem to render it advisable to 

 ;ive at this tnne, a brief abslract of some portion 

 )fthe results. Tlie civil history of the insect, as 

 »ell as the scientific descriptions, with many other 

 letails, are reserved for the final paper. 



Tlie Hessian fly, which has so long been con- 

 ipicuous for its depredations on the wheat crops ot 

 .his country, is a two-winged insect of the genus 

 LasiopUra or Ctcidomyia, (•'^f'g'. and Latr.) and 

 was first scientifically described by the late Mr 

 rhoinas Say, (Jour. Acad. Nat Sci. Phil. 1817, i. 

 15,) who jiave it the specific name of Destructor. 

 The pojiular name was first used by Col. George 

 nlorgai), "t Prospect, N. J., on the supposition that 

 he insect was introduced into this country among 

 he straw brought by the Hessian troops who came 

 ,ere in the service of Great Britain, during the 

 •»ar of the Revolution. This supposition has been 

 ejected by mo?t entomologists, chiefly perhaps, 

 I'Ccause I'.n extensive and apparently thorough in- 

 uiry made in various parts of Europe a few years 

 fler, resulted in the uncontradicted conclusion 

 hat the insect was wholly unknown in that quar- 

 or of the world. I am not prepared to assert that 

 his insect was introduced in the manner above 

 uppoied. but it may be shown that it is highly 

 ■robable that it was unknown here before that 

 ime i that it now exists in Europe, and has 

 robali'.y been there for centuries. 



In the Ekmtnts iT Jlfrricidlure, par Dithamel du 

 Honeeau, Paris, 1771, "2 tomes, 12 mo., is a etate- 

 nent fiom M. do Chateauvieux, of which the fol- 

 owing is a translation: — "Our wheat [in the 

 leigiiborhond of Geneva] has sustained the present 

 lonlh of May, 17.5.5, an injury from which the 

 ;rain cultivated by the new husbandry has not 

 een exempt. We found upon it a number of 

 '- mall white worms, which eventually turned to a 

 hestnut color: they fix themselves within the 

 saves, and gnaw the stalks. They are commonly 

 ound bef.vecn the first joint and the root: the 

 talks ua which they fasten grow no more; they 

 ecorne yellow and dry up. We suffered the 

 ame iijury in 17;i2, when these insects appeared 

 ^n tiie iiiiddiu of May, and did such damage that 

 he crops were almost annihilated." This pa.?sage 

 »8S quoted by Col. .Morgan, (Carey's Ainer. Mus. 



1787. i, .530,) in the bcliof that the insect described 

 in it was the Hessian tly. The description is loo 

 imperfect to authurizo a positive assertion, but 

 there seems to be little doubt that his opinion is 

 correct. 



In 183.3, Mr Dana sailed for the Mediterranean 

 in the U. S. ship Delaware. .Vn opportunity was 

 thus aflbrdcd him to make personal exploration for 

 the Hessian fly among the wheat inc\An of the old 

 world ; a work for which he was well prepared by 

 his thorough aci|uiiintance with this insect in its 

 various stages. His examinations were rewarded 

 with the most gratifying success, for they proved 

 that the Hessian Jlij is rt7i inhiibitunt of Europe. — 

 On the 13th of March, 1834, and subsequently, he 

 collected several larva- and pupa', from wheal 

 plants growing in a field on the island of .Minorca 

 From these pupee, were evolved on the Kith of 

 March, 18 54, two individuals of an insect which 

 his recollections, faided by a drawing of the Hes- 

 sian fly with which he was provided,) enabled him 

 to pronounce to be the Cccidoniyia Destructor. 

 More of the perfect insects were evolved in llie 

 course of the month, one of which deposited eggs 

 like those of the Hessian fly. In letters dated 

 Mahon, April 8 and 21, 1834, Mr D. sent nic five 

 of the insects and several of the pupte. They ar- 

 rived in safely, and alter a careful examination, I 

 i!aw no good reason to doubt the identity of this 

 insect with the Hessian fly. The Mahonese as- 

 serted that the insect had been there from time 

 immemorial, and often did great damage both there 

 and in Spain. On the 28th of April, 1834, Mr D. 

 collected from a wheat field just without the walls 

 of the city of Toulon, in France, several pupsp and 

 one larva like those before obtained. On the 4th 

 of June, 1834, he obtained similar pupse from a 

 wheat field near Naples. About the period of Mr 

 Dana's investigations in the south of Europe, at- 

 tention was turned to the injury caused by certain 

 larvse among the wheat in Hungary. It appears 

 now to be commonly believed, that their parent in- 

 sect is cither our Hessian fly, or an animal very 

 closely allied to it. 



I have searched in vain for any traces of the 

 Hessian fly in this country before the Revolution. 

 The Rev. Jared Eliot, in his "Essays upon Field 

 Husbandry in New England," Hoston, 1700, treats 

 of the culture of wheat, but makes no allusion to 

 any insect having habits like those of the He.ssinn 

 fly ; neither does Kalm, the naturalist, who trav- 

 ellcd in this country about 17.50. 1 am therefore 

 inclined to consider the common opinion of the 

 origin of the insect quite as probable as any other 

 which has been advanced. 



In this part of our country, wheat is usually 

 sown about the first uf Sepleiiiber. Soon after the 

 plants are up, the Hessian fly begins to lay her 

 eggs upon them, and continues her operations for 

 several weeks. She deposits her eggs on the up- 

 per surface of the leaf (i.e. the tif^ula, or strap- 

 shaped portion of the leaf) of the plant. The num- 

 ber on a single leaf is often twenty or thirty, and 

 sometimes much greater. In these cases many of 

 the larvs must perish. The egg is about a fiftictli 



of an inch long, and four hundredths of an inch in 

 diameter, cylindrical, translucent, and of a palo red 

 color. In about four days Iho egg hutcliea; the 

 young larva creeps down the leaf, enters the shcalji, 

 niid wiili the head downwards, faslenii upon the 

 tendir culm oor stalk, generally just above some 

 joint. The larva appears to feed solely on the 

 sap of the plant; it does not gnaw the stalk, and 

 never enters it, but is gradually imbedde<l in it aa 

 the plant matures. Having taken its post, the lar- 

 va is stationary ; il gradually loses its rcdilish col- 

 or, becomes translucent, and clouded with while 

 S|int6, and when near maturity, the central part 

 within is of a greenish hue. In about five or six 

 weeks, (or longer if the season is cold,) the larva 

 begins to assume a brownish tinge, and soon is of 

 a bright chestnut color, when the insect may be 

 said to have reached the stale of pupa. It has 

 then some resemblance to a flax-seed. The outer 

 skin of the larva becomes the puparium of the pu- 

 pa. The wheat plant is injured by the loss of sap, 

 but principally by the pressure of the larvte and 

 pupa; upon the culm. A single larva will do little 

 harm, and may even be useful by stimulating the 

 plant to throw out side shoots; but five or six of 

 them arc sufticienl seriously to check the growth 

 of the plant, or perhaps to destroy it entirely. 



During the winter the insect is in the pupa 

 state, near the root of the wheat plant, and usually 

 a little below the surface of the earth. In April 

 and May we again find the Hessian fly laying egga 

 on the young wheat, both that which was sown ia 

 the autumn previous and the spring wheat, which 

 is of course recently up. The larvoe from these 

 eggs become pupse about the middle of June. 



There is no difficulty in tracing the insect as far 

 as the state of pupa, and to this point its history is 

 satisfactorily ascertained. Regarding the periods 

 of the evolution of the perfect insect, there is, how- 

 ever, some obscurity, which numerous observations 

 have not wholly cleared up. The difficulty results 

 in part from the fact that in this region, a very 

 large proportion, probably more than nine tenths, 

 of every generation of the Hessian fly, is destroyed 

 by parasites. A great part of the pupa: which 

 may be collected will evolve some parasitic insect, 

 instead of the Hessian fly. It is certain that some- 

 times the pupee, which became so in June, evolve 

 the perfect insect in October following, and that 

 other pupsB of the same date will not evolve the 

 perfect insect until October of the year succeed- 

 ing. The following seems to mc the probable his- 

 tory of the matter. The pupiE which became such 

 in the autumn, evolve the perfect insect, partly 

 during the next spring, and partly in the summer 

 and autumn following. The pupa;, which became 

 such in and about June, evolve the perfect insect 

 partly during the next autumn, and partly during 

 the year succeeding. 



Parasites. — There are in this region, four prin- 

 cipal parasites of the Hessian fly, one of which at- 

 tacks the eggs and the other three the pupte. They 

 are all minute Hyinenoptera. 



1. The egg-parasite is a species of PlatygasUr, 



