THE HOLLY-FLY 21 



For a long time I could find no trace of this insect 

 egg, larva, pupa or fly during late summer and autumn. 

 The flies emerged in June, but the blisters never appeared 

 on the holly-leaves before November. What went on 

 during the interval ? Was there perhaps a second brood, 

 fed upon a totally different plant ? Every likely method 

 of observation was tried without success. Once our atten- 

 tion was directed to little dots on the under side of the 

 holly-leaves, which looked like the holes made by a small, 

 egg-laying fly, but these turned out to be only the pricks 



FIG. 5. Holly-fly, magnified. 



of other holly-leaves, made in a season of high winds. 

 The puzzle was at last solved by Mr. T. H. Taylor, who 

 discovered the young and minute larva in September, and 

 thus supplied the part of the story which had escaped our 

 notice. The egg is laid in June by the newly emerged 

 female fly on the under side of the midrib of a holly-leaf 

 lately come to its full size, never on an old leaf. The 

 place where the leaf is pierced (probably by the larva) 

 afterwards becomes conspicuous as a red spot. As soon 

 as it hatches out, the larva bites its way into the vessels 

 of the midrib, and no doubt finds itself very well off there, 

 getting complete protection and an abundant supply both 

 of liquid food and air, without trouble or anxiety. It 

 travels slowly along the vessels, and may take four months 



