Vol. Xxix] ENTOMOLOGICAL NEWS. 143 



Data Concerning Flies that Frequent Privy Vaults 



in Montana (Dip.). 

 By R. R. PARKER, Bozeman, Montana. 1 



As a part of the fly investigations conducted by the Mon- 

 tana State Board of Entomology at Laurel, Montana, during 

 the season of 1914, experiments were carried on to obtain 

 data concerning the species of flies frequenting privy vaults. 

 Local conditions were discussed in the First Biennial Report 

 of the Board, pages 36 to 50. 



The most detailed results were obtained from a trap con- 

 structed to cover the entire back of a privy, the vault of which 

 was open in the rear. The excavation was about three feet 

 deep. The seats were uncovered and the door always open. 

 After the trap was in place the flies had ingress by means of the 

 doorway and the open seats and could escape either by the 

 reverse course or by the trap opening in the rear of the vault. 

 In the latter ca?e they were captured. The results ; therefore, 

 showed the species present and their comparative abundance, 

 but not the total number of flies entering the vault. 



The flies for examination were captured in small Hodge 

 traps placed above holes bored through the board forming the 

 top of the large trap. These traps were collected and new ones 

 substituted each day except Sunday, the catches for Saturday 

 and Sunday being counted as one. The experiment was con- 

 tinued for 32 days, from July 20 to August 21. An accurate 

 record was kept of the number of males and females of each 

 species. At the conclusion of the experiment a large number 

 of dead flies were removed from the large trap, but owing to 

 their poor condition it was impossible to separate the males 

 and females and in the genera Calliphora, Lucilia, Fannia and 

 Sarcophaga specific determinations were not attempted. The 

 results are shown in the accompanying table. 



The total catch was c;6/6 flies, 8330 from the Hod^e tra<>s 

 and 1346 from the large trap. The number of species in- 

 cluded was 26, Muscidae, 13; Anthomyidae, 4; Sarcophagi- 

 dae, 3 ; Syrphidae, 2 ; Tachinidae, i ; Culicidae. 2 ; and Orta- 

 lidae, i. The reader should consult the table for the species 

 totals and species percentages of the total catch. 



The data show one fact that is common to all the species, 

 namely, that the females greatly predominate. This is espe- 

 cially apparent in Lucilia sericatc (Meigen) and L. caesar 

 (Linnaeus'), the former showing a ratio of I male to 678 fe- 



1 Contribution from the Laboratory of the Montana State Board of 

 Entomology, State College, Bozeman, Mont. 



