238 



Who shall decide, when Doctors disagree \ 



Vol. V. 



of the plant." But, unfortunately, according 

 to Miss Morris, the C. destructor does not 

 pass its larva-existence in the interior of the 

 stem, but merely travels throucfh it in its 

 progress from the grain to its residence in the 

 sheath of the blade. To make it " agree 

 very well" with Miss Morris's discovered 

 habits of the wheat-fly, Doctor Coates should 

 have shown that this "splendid beetle" de- 

 posits its eggs in the seeds of the elder — 

 that they are planted with them — spring 

 into life together, and that the young insect 

 " grows with the growth, and strengthens 

 with the strength" of the plant. This he 

 has not done, and perhaps will not do, as 

 these " luxuriant shoots" spring from old roots, 

 and not from seeds. 



After quoting from Say^s account, that 

 "the perfect fly appears early in June, lives 

 but a short time, deposits its eggs, and dies — 

 the insects from these eggs complete the 

 history by preparing for the winter brood" — 

 the Doctor remarks, that " the words would 

 seem to imply that there are two broods — 

 one for summer, and one for winter. If 

 ' preparing for the winter brood' means lay- 

 ing the eggs which are to produce them, why 

 are not the flies seen in the end of October, 

 before which time the sheaths of the leaves, 

 and the straw itself of the winter-wheat, do 

 not exist, and at which period no fly, of any 

 description, is to be met with in the fields ]" 



These assumptions of Doctor Coates, if 

 correct, certainly place Say in a dilemma ; 

 but they are no less unfortunate for the dis- 

 covery of his friend 3[iss Morris — for if 

 " the sheaths of the leaves" do not exist at 

 the end of October, it is as impossible for the 

 larvae to inhabit them on the one supposition, 

 as the other. Perhaps he may say that the 

 worm does not leave its nidus in the grain 

 till after the period spoken of; for he says, 

 " the young worm is then below the surface 

 of the earth, in a substance that is not frozen, 

 and which supplies him with food." But I 

 will appeal to every observant farmer to say, 

 whether the " sheaths" and the " straw" are 

 not sufficiently matured for the purposes of 

 the fly, before the end of October. Whether 

 they have not often seen the larvae in the 

 sheaths before that period. — Yes — ten 

 thousand eye-witnesses can testify to the 

 truth of this — and that their wheat-crops 

 have been literally eaten up before the end 

 of October. 



But, " why are not the flies seen in the end 

 of October ?" By omitting the first word, this 

 question will answer itself: " Are not the flies 

 seen in the end of October 7" 



According to Miss Morris, and her en- 

 dorsers, it appears that the larva3 of the C. 

 destructor "enter the pupa state about the 

 beginning of June." This agrees very well 



with what Say tells us of the summer breed, 

 and is probably correct. But when early- 

 sown wheat becomes infected with the fly, 

 the larvse pass into the pupa state in autumn, 

 and, I believe, very often come out in flies 

 sufficiently early to deposit other eggs before 

 winter. 



The following transcript is from my fifth 

 number of the Farmers' Cabinet, Vol. 1, p. 

 287, and was written about the time Miss 

 Morris commenced her discoveries. 



" All the observations which I have been 

 able to make, have confirmed me in the opi- 

 nion that they (the cecidomyia destructor) 

 deposit their effgs at various seasons of the 

 year, subject to be influenced by circum- 

 stances — and that the duration of the seve- 

 ral stages of their existence depends upon 

 season and temperature. In warm weather 

 a few months, or even weeks, may be suffi- 

 cient to produce the fly from the egg — but 

 the progress of its metamorphoses will be re- 

 tarded, or entirely arrested, by cold weather. 

 Last spring (1836) the flies* were very nu- 

 merous in my wheat field, when I sowed 

 clovor-seed, in the beginning of the fourth 

 month. They could be seen to rise at almost 

 every cast of seed, and would fly forward, 

 and settle down again in the same way as 

 grasshoppers are observed to do. These 

 had probably come out of the winter pupa 

 in the opening spring, and were about to 

 deposit the eggs, which, after destroying the 

 crop, produced other flies, in the sixth month. 

 This would allow a period of about two 

 months for the completion of these several 

 changes. 



" When the eggs are laid in early autumn, 

 the insects will become pupte before winter, 

 ready to emerge, early in the spring, and 

 prepared for new devastations, in the way 

 which I have just mentioned. 



" Observations are still wanting to deter- 

 mine whether the larvse of eggs laid later in 

 the fall can endure the winter in that state 

 — or whether the egg can remain, and hatch 

 in the spring. I think it probable that nei- 

 ther the egg nor the larva can survive the 

 frosts of winter, unless protected from intense 

 cold by a mantle of snow, as was the case in 

 the winter of 1835-6. The autumnal pros- 

 pect exceeded any thing we had for a long 

 time witnessed — the dreadful reverse, at 

 the ensuing harvest, will be long remem- 

 bered. The fall was favourable to the growth 

 of wheat, but it was also favourable to the 

 propagation of its greatest enemy — the fly. 

 Its ravages were scarcely perceptible in the 

 fall, yet it was undoubtedly there. Whether 



* To satisfy myself of their identity, I caught seve- 

 ral of them, and submitted thom to a microscopical 

 examination and comparison with Say's description, 

 and with specimens of the preceding summer. 



