Relationship between the amount of CO2 and the collection of Tabanidae in Malaise traps

The attractiveness of different amounts of carbon dioxide for Tabanids was compared based on collections in Mississippi in Malaise traps in which carbon dioxide was released at rates of 0, 100, 1000, 2000, 3000, 4000 or 5000 ml/min. The collections of 10 of the 18 species taken were statistically analysed. Analysis of variance based on the transformation of the data to log. (n+1) was the most satisfactory of the 4 transformations studied. Regression analyses were made with 9 models; the most satisfactory model was log. (Y+1)=a+bX+cX2, where Y is the number of flies and X the rate of release of carbon dioxide. The resulting regression equations show that rates of release of carbon dioxide above 4000 ml/min reduce the number of flies collected. A black object used as an alternative bait did not attract some species but was the equivalent for other species of a rate of carbon dioxide release of 100 ml/min.