150 OLIVE C. LODGE. 



The varnishes used were (a) gelatine heated in water, which was first painted 

 over the eyes, and when nearly dry a drop of absolute alcohol was added to coagulate 

 it, and finally, when quite dry, this was painted over with water-proof Indian ink, 

 to make it opaque ; or (b) a saturated solution of shellac in absolute alcohol in which 

 light green stain was dissolved was painted over the eyes.* 



The eyes were examined very carefully before and after each experiment, to see 

 that they were completely covered, for the flies were sometimes able to rub up the 

 edge of the varnish, in which case the whole cap of varnish peeled off. If this was 

 found to have happened, the results were rejected. 



In these experiments the flies in nearly all cases behaved rather abnormally, 

 being less active than normal flies and spending a great deal of time, especially at 

 first, in trying to rub off the varnish. They paid little attention to the baits, although 

 they sometimes came down to feed. They appeared able to tell attractive from 

 repellent foods, feeding upon the former, though in less numbers than normal flies, 

 and leaving the latter alone. 



Similar results were obtained when Calliphora and Lucilia were used. 



Confined house-flies with antennae cut off. 



The flies after their antennae were cut off appeared able to detect differences in 

 foods, and to be able to distinguish between attractive and repellent substances, 

 coming to feed on foods which were attractive to normal flies, although they appeared 

 to take less interest in them than normal flies, and avoiding those which were disliked. 

 This was particularly noticeable when a few drops of the different mineral and tar 

 oils were added to the baits. It was also noticed that the antennae-less flies seemed 

 to lose to a certain extent their sense of balance, falling over on their backs more 

 frequently than normal flies ; they also experienced greater difficulties in getting 

 up again. 



Very similar results were obtained with blow-flies. (Lucilia and Calliphora). 



Note on the life-history of Fannia. 



In order to discover the length of time of the larval and pupal stages of Fannia, 

 the eggs were kept under observation ; some began to hatch after one day, and 

 all had hatched by the 3rd day. Unfortunately oviposition was not actually observed, 

 hence the eggs may take longer than 1-3 days to hatch out. It was noticed that 

 if they became too dry, they did not hatch out, and that if they were moistened 

 with a few drops of water they hatched more quickly, the longitudinal split often 

 beginning immediately the water was applied. The larval stage lasted 11-21 days, 

 giving an average of 14-15 days. The pupal stage lasted 13-34 days, giving an 

 average of 21-22 days. The largest number of flies emerged, however, after 19-26 

 days. The total number of flies which emerged was 70-100. 



*It was not at all easy to make the varnish remain on the eyes, chiefly because the 

 flies were always trying to rub it off. However, after various trials the above two 

 comparatively satisfactory ones were obtained. My thanks are due to Mr. P. M. Howlett 

 for many useful suggestions in connection with these varnishes. In order to prevent 

 the flies from rubbing off the varnish before it was dry, they were at first held in the hand, 

 but as drying was often a long process, they were often placed in paper pillories for 

 convenience in handling. 



