Explanation of Plate XV. 



Fig. 1. Down the left-hand side of the vertical strip of pftj>rr the 

 cork from a tube of methyl eiigenol has beei] rubbed, 

 so as to leave a smear, and there is a smaJ] circ.ular 

 patch of methyl eugenol made in the same way a.^ the 

 bottom right-hand corner of the paper strip. To the 

 right of this there is a similar streak of iscieugenol, 

 and on the extreme right a streak of er.genol. The 

 flies are practically all Dacus zonatus (there Y/vre two 

 D. diver sits on the middle streak), and approao.hed 

 up-wind from the right of the picture. 



2. The same surface (a cork mat) a week afterwards. 



