74 



THE CANADIAN ENTOMOLOGIST 



from the substance in which they have been feeding. Hutchison 

 (I.e.) found that the majority of the pupae were scattered about 

 the drier margins of the heaps of horse-manure, sheltered by the 

 overhanging straw, and that whereas, in one heap, he found about 

 9000 pupae in this position, not more than 100 were found below 

 the soil. In this connection the following observation appears to 

 be worthy of record. 



Following the experiments which I carried out (1914) on the 

 control of the larvae by various insecticides, it was decided to 

 examine the soil around and beneath the untreated and conse- 

 quently natural heap of horse-manure with a view to ascertaining 

 the distance and depth travelled by the larvae prior to pupation. 

 Also it was desired to discover whether any of the insects were 

 overwintering in the pupal state; to this aspect of the question I 

 shall return later. 



The manure was removed on May 13th and the soil subjacent 

 to and around the site of the pile was carefully removed and an 

 approximate record was kept of the numerical abundance of the 

 puparia at the different depths below the surface of the soil to a 

 distance of about four feet around the site. This task was carried 

 out for me by Mr. S. N. Lord, to whom my thanks are due. The 

 results of this examination of the soil, which was a sandy loam, 

 are represented diagramatically in the accompanying figure. 



feer 



* 3 



Felt 

 4 



Fig. 7. — Diagrammatic section through heap of manure and subjacent soil to show the migration 



of the larvae of Musca domestica. The drawing is to scale, distance and depth in feet being 



indicated. The black dots in the soil represent the puparia. (Original). 



