67 



Entomoloj;ists — under the name of the Destructive Midge (Ci'cidomyiii <lf^trudor). "This 

 insect — Dr. Fitch relates — as a L^cncral rule passes throuu'h two j^enerations annually. The 

 first of these occupy the autumn, winter and fore part of spring, and is reared at the roots 

 of the young gr.iin slightly under the ground. The second occupies the remainder of the 

 spring and summer, and is nurtured in the lower joints of the straw. The time when its 

 several changes occur, however, is not perfectly uniform, being varied by the climate, the 

 state of the weather and perhaps other contingencies, and it is not improbable that individual 

 specimens, placed in circumstances unfavourable to their developement, in some instances 

 have their growth so much retarded as to require even a whole year to complete their meta- 

 morphoses. In the ordinary course of nature, therefore, our crops of winter wheat are liable 

 t,o two attacks of the Hessian fly, one generation reared at its roots producing another which 

 occupies, the lower joints of the stalks. Thus the larvae and pupa' are present in it almost 

 continually, from the time the tender young blades appear above the ground in autumn till 

 the grain ripens and is harvested the next summer. Our spring whe;!t, on the other hand, 

 can rear but one brood of these insects ; they consequently resort to it but little if at all. 

 Nor can the Hessian fly sustain itself except in districts where winter wheat is cultivated, in 

 which to nestle during the autumn and winter." 



The eggs of the autumn generation are deposited by the female fly generally early in 

 September, in the young fall wheat, in a crease of the leaf. Twenty or thirty eggs are laid 

 on a single leaf, and these hatch out in about four days if the weather be warm. Mr. Tilgh- 

 man, of Maryland, has published in The CidtiraUir, of May, 18-H, the following minute and 

 interesting account of the mode in which the eggs are laid : " By the second week of Octo- 

 ber, the first sown wheat being well up, and having generally ])ut forth its second and third 

 blades, I resorted to my field on a fine warm forenoon to endeavour to satisfy myself by 

 ocular demonstration whether the fly did deposit the egg on the blades of the growing plant. 

 Selecting a favourable spot to make my observation, I placed myself in a reclining position in 

 a furrow, and had been on the watch, but a minute or two before I discovered a number of 

 small, black flies alighting and sitting on the wheat plants around me, and presently one 

 settled on the ridged surface of a blade of a plant, completely within my reach and distinct 

 observation. She immediately be^an depositing her eggs in the longitudinal cavity between 

 the little ridges of the blade. I could distinctly see the eggs ejected from a kind of tube or 

 sting. After she had deiiosited eight or ten eggs, I easily caught her upon the blade and 

 wrapped her up in a piece of paper. After that I continued my observations on the flies, 

 caught several similarly occupied, and could see the eggs uniformly placed in the longitudinal 

 cavities of the blades of the wheat, their appearance being that of minute reddish specks." 

 These eggs are computed to be about one-fiftieth part of an inch in length. 



When hatched from the egg, the next proceedings of the insect are thus related by Mr. 

 Herrick : — " The little wrinkled maggot or larva creeps out of its delicate membraneous egg 

 skin, crawls down the leaf, enters the sheath, and proceeds along the stalk, usually as far as 

 the next joint below. Here it fastens lengthwi.se, and head downwards, to the tender stalk, 

 and lives upon the sap. It does not gnaw the stalk, nor does it enter the central cavity 

 thereof ; but as the larva increa.ses in size, it gradually becomes embedded in the substance of 

 the stalk. After taking its station the larva moves no more, gradually loses its reddi.sh colour 

 and wrinkled appearance, becomes plump and torpid, is at first serni-transluccnt, ami then 

 more and more clouded, with internal white spots ; and when near maturity the middle of the 

 intestinal part is of a greenish colour. In five or six weeks (varying with the season) the 

 larva begins to turn brown, and soon becomes of a bright chestnut colour, bearing some re- 

 semblance to a flax-seed." Two or three larviv, thus embedded in a stalk, serves to weaken 

 the plant and causes it to fall down, or to wither and die. 



In this condition, the " flax-seed state," as it is usually termed, the insect remains all 

 winter. Regarding the structure and formation of this peculiar appearance there has been 

 much controversy, into which we need not enter here. Suffice it to say, that some have held 

 the opinion that the larva spins its cocoon which bears this form ; others, that it is the hard- 

 ened outer integument of the worm, separated from the insect, which remains within ; others 

 again, and notably, the late Mr. Walsh, that the pupal cocoon is e.vuded from the larva. 

 Whatever may be the process, in this condition it remains till the warm days of spring arrive, 

 whenjthc insect completes its pupal state, and finally comes forth as a tiny two-winged fly. 

 (Fig. 50.) 



