358 



LL. LLOYD. 



was then fastened in sandwich manner between a pair of white glass microscope 

 sHdes and the upper one was hghtly smeared with adhesive. These were placed in 

 the cage as described above and their positions were interchanged twice, counts 

 being made each time. The total exposure was four hours, with the sun shining 

 brightly ; 1,041 flies were caught, and their distribution is shown in diagram 5. 

 Yellow trapped 60 per cent, of the total ; the yellowish-green was attractive, and 

 the tomato leaf less so. Red, blue, white, and in this case orange also, gave negative 

 results. 



Diagram 4. (See Experiment 3. 



Diagrams. (See Experiment 11. 



The large numbers trapped in these short exposures b}' the opaque yellow, com- 

 pared with the numbers trapped by the yellow solutions, suggests that the former 

 is more attractive, and the following experiments seem to confirm this. 



Experiment 13. 



December 22nd-29th ; five glass tubes twelve inches long and half an inch in 

 diameter were taken. Four were filled with a solution of -g^^- per cent, orange G., which 

 in a column of this diameter appeared to have the same tint as the ^-|^ per cent, solution 

 in a one inch column. The fifth tube was lined with yellow paper. All were smeared 

 with adhesive and suspended around an infested tomato plant ten inches high on 

 staging in the greenhouse. The clear tubes trapped 178 flies, an average of 44 each, 

 and the opaque one 91. At the end of the experiment there remained on the plant 

 17 flies only. 



The relative attractions of tomato foliage and a yellow surface are shown in the 

 following experiments. 



Experiment 14, 



December 23rd-31st; a sheet of yellow paper, 7 in. by 8 in., was sandwiched 

 between two sheets of glass of the same size and the trap was coated with adhesive on 

 both sides. This was then suspended vertically facing north and south, and a lightly 

 infested tomato plant about one foot in height was placed on each side of it at a 

 distance of a foot. A third similarly infested tomato plant was placed at a distance 

 of six feet. All the plants were recently infested, and no flies emerged on them during 

 the course of the experiment. There were, however, a number of infested plants 

 in the greenhouse on which flies were emerging, and these had access to the three 

 plants and the trap. Eight days after the experiment had been set up the plant 

 to the north held 33 flies and the north side of the trap 602, the plant to the south 



