THE WHEAT MIDGE. 93 



crawling about, and ere many days become cased larvae — the yel- 

 low worms being shorter than the semi-transparent pod in which 

 they are inclosed. They may now be kept for months, even in a 

 dry, stove-warmed office, without losing their vitality. Then, 

 upon placing them between the folds of a wet cloth, they will 

 next day be found actively crawling about within the cloth, till 

 reaching its outside they with a skip throw themselves away from 

 it, not one of them leaving a carse or empty skin behind in the 

 cloth." 



Mr. D. J. Browne, in the Patent Office Report for 1854, page 

 74, says, "towards the last of July or beginning of August, the full 

 grown maggots cease eating, and become sluggish and torpid, 

 preparatory to shedding their skins, which takes place in the 

 following manner : — The body of the maggot gradually shrinks 

 in length within its skin, and becomes more flattened and less 

 pointed, as readily may be seen through its delicate transparency. 

 This torpid state lasts only a few days, after which the insect 

 casts its skin, leaving the latter entire, excepting a little rent at 

 one end of it. These empty cases or skins may be found in great 

 abundance in the wheat ears after the moulting process is com- 

 pleted." 



Apparent Periodicity in the visits of the Wheat 

 Midge. 



158. A singular apparent regularity in the periods of its re- 

 currence in vast numbers so as to prove eminently destructive, 

 has been hinted at by Dr. Fitch in 1 844.(1) When these instances 

 of periodicity are associated with its late destructive depredations 

 in the United States and Canada, they seem to acquire a peculiar 

 although perhaps speculative interest. Its appearances at differ- 

 ent periods are as follows : — 



(1) See succeeding paragraph. 



