A MAGGOT TEAP IN PRACTICAL USE, 



11 



not as thorouglily as on the former occasion, but there were found at 

 the fresher end of the pile at least four nests of several hundred puparia 

 each. It is not possible to estimate the percentage destroyed, but it 

 was quite plain that the trap was not as effective during the autumn 

 as in the summer. This may have been due partly to carelessness in 

 the matter of watering the heap, but more probably to the lower air 

 temperatures of this period. When the outside temperature is low, 

 the difference between the air and the temperature of the manure 

 heap is so great that the larvae will not leave the heap; and if the low 

 temperatures prevail for a long period the larvge will eventually 

 pupate in the manure. The following experiment shows the effect 

 of low air temperature. This experiment was conducted at New 

 Orleans, La., in December, 1913. A small wire basket was filled 

 with fresh horse manure on December 1 and was continually exposed 

 to flies. The number of larvae caught and the temperature during 

 the period are tabulated below. 



Experiment to shoio effect ofloiv air temperature in preventing migration of house-fly 

 larvse, Neiv Orleans, La., December, 1913. 





Number 

 of larvas 

 caught. 



Kini- 

 mum 

 tempera- 

 ture. 



Maxi- 

 mum 

 tempera- 

 ture. 



Mean 



temperar 



ture. 



Ijpc. 2 



12 



15 



47 



199 



745 



° F. 



57 



56 



57 



56 



57 



48 



40 



32.5 



34.5 



38 



41 



47 



58.5 



49 



50 



"i5 . 5 

 ;i 



° F. 



74 



67 



68 



73 



70 



61 



61 



50 



56 



59 



65 



68 



73 



66 



62.5 



69 



60 



5S 



" F. 

 65.5 



3 



61.5 



4 



62.5 



5 . . . 



64.5 



6 



63.5 



7 



55 



8 



14,000 







1 



43 



465 



1900 





ft 



41.7 



10 



45.3 



11 



48.5 



12 



53 



13 



53 



14 



65.8 



15 



1700 

 115 

 185 

 160 



57 5 



16 



56 2 



17 



60.5 



18 



57 8 



19 



54.5 







' Approximate. Counts of Dec. 8 and 15 include catch of preceding day. 



Probably most of those that were caught on December 8 had 

 migrated during the night of December 6. Not much migration from 

 the manure takes place during the day, because of the maggots' nega- 

 tive reaction to light; therefore the minimum temperature is probal)ly 

 more signififjirit tluiri tlu! daily mean temperature. It will bo seen 

 from the tahlc. that minimum temperatures of 40° F. or less will stop 

 all raigratifiii from tlio heap. 



It may be suid, then, tliat tlie maggot trap has another defect in 

 tliut it iH not efFcirtive wlien teinperatures are low, and that it is not 

 at all effective when the air temperature is below 40° F. 



