THE CANADIAN ENTOMOLOGIST. 73 



of the pest and advise methods of control. All of this goes to 

 emphasize the necessity of investigating carefully, and as 

 thoroughly as possible, using proper judgment of course, insects 

 and their attacks upon vegetation, regardless of whether they are 

 at the time injurious or not. It may be that, even at that very 

 time, the insect is seriously injurious, but its injuries are of such 

 an obscure nature as to be overlooked entirely or perhaps confused 

 with those of some of the older and better known pests. Entomo- 

 logical investigations cannot be undertaken, carried through, and 

 completed by contract, as the erection of buildings, construction 

 of railways, or excavating of canals, but opportunities must be 

 judiciously seized upon, and if the problem is followed faithfully 

 wherever it may lead, one will be surprised at the number of 

 instances like the foregoing, when the final outcome has more than 

 justified the investigation. 



NOTES ON THE PUPATION OF THE HOUSE-FLY (MUSCA 



DOMESTIC A) AND ITS MODE OF 



OVERWINTERING.* 



BY C. GORDON HEWITT, D. SC. 

 DOMINION ENTOMOLOGIST, OTTAWA. 



The migratory habit of the larvae of Musca domestica evidenced 

 prior to pupation has been observed by most of the investigators 

 who have studied the insect's life history, and these observations 

 have been collected by Hutchison (1914). Levy and Tuck (1913) 

 appear to be the first workers to call attention to the practical 

 value of this habit in fly control, and Hutchison has extended the 

 work along lines that will undoubtedly provide us with an additional 

 means of control of no little value. The principle involved is the 

 capturing of the mature larvai leaving the manure to pupate, in 

 accordance with their usual custom, either in the cooler outer 

 portions of the piles or in the subjacent soil. 



The migratory habit of the larva has also another interest, 



namely, its relation to the suppression of flies breeding in the 



usual type of insanitary privy and in latrines. While a few isolated 



observations have been made in India and elsewhere, I do not 



know of any exact record of the extent to which the larvae migrate 



* Contribution from ihe Entoinological Branch, Department of Agriculture, 

 Ottawa. 



March, l!)!.", 



