June, '16] EVANS: BREEDING HABITS OF COMMON HOUSE-FLY 355 



that the house-fly breeds there, the adults of Drosophila being taken, 

 by those who do not know, to be the young of the house-fly. Manure 

 piles in the vicinity of the garbage cans studied were examined when 

 possible and in every case the house-fly in all of its stages was found to 

 be abundant. In the examination of manure piles the pupae as well 

 as the larvae about to pupate were most abundant about the outer 

 edge of the piles, in the loose straw or even in the earth. In one case 

 where the manure was thrown into a low wagon the larvae migrated 

 to the bottom of the wagon box. where they fell through the cracks and 

 buried themselves in the top layer of earth preparatory to pupation. 

 Migration of the larvae of the house-fly has been studied by 

 various writers (1) and is recorded here merely as additional facts 

 observed. 



Another point noticed was that the larvae avoided the deeper parts 

 of the piles which were wetter from the seepage of moisture from the 

 upper layers. This will be more fully discussed under the reaction 

 of larvae to moisture. 



Although no larvae were found in the rubbish examined not enough 

 was studied to warrant forming an opinion. By rubbish is meant any 

 trash other than that which might be classified as garbage or manure. 

 The manure studied in all cases where not otherwise mentioned was 

 the refuse from barns where horses were quartered. 



The lack of the larvae of the house-fly in garbage together with its 

 abundance in stable manure seemed- to indicate that there was some 

 difference between the two substances which in the case of the manure 

 furnished an optimum condition for fly breeding and was prohibitory 

 in the case of the garbage. A chemical difference seemed the logical 

 one to assume. Since the substance which was prohibitory in the 

 garbage might prove to be a good larvicide an effort was made to deter- 

 mine it if possible. Quantities of garbage and stable manure were 

 brought into the laboratory for study. When tested the manure was 

 found to be alkaline while the garbage was acid. As ammonia is 

 known to be present in manure several tests were made to determine 

 the relative amount present. The tests showed the amount to vary 

 with the length of time that the manure had been standing. Manure 

 which had been standing no longer than thirty minutes was found to 

 contain .647 of a per cent. That which had been standing for a longer 

 period contained less; even as little as .314 of a per cent.^ In cases 



^ These tests were made in the chemical laboratory of the University of Colorado. 

 The writer is indebted to Professor Harry Curtis for the privileges of the laboratory 

 as well as suggestions as to methods. I wish also to acknowledge the following 

 assistance: Professor T. D. A. Cockerell for several important references as well as his 

 kindly interest in the work; Professor A. H. Peebles for the loan of a book; and Pro- 

 fessor Francis Ramaley for reading the paper for me. 



