CHAPTER I 

 A General Acquaintance with Leaf-mining Insects 



Green leaves are the world's dependence for food produc- 

 tion. Day by day, as the sun shines on them they build 

 up the organic substances by which all men and all animals 

 live. Directly or indirectly they feed both great and small. 

 Their consumers range in size from the great elephants of 

 the tropical jungle down to the little tenants of single leaves 

 that are the subject of this volume. 



Leaf-miners are among the smallest of plant-eating 

 animals. Most of them find both sustenance and shelter 

 within the confines of a single leaf— often within a small 

 portion of a leaf, between its upper and its nether epidermis. 

 Their food is the thin stratum of green tissue that lies, 

 like coal in a mine, outspread in a seam between two worth- 

 less adjacent strata, and the insects get it and dig it out for 

 use. That is why we call them miners. 



Leaf-miners are everywhere. In any lane or fence-row 

 they may be found by one who will take the trouble to look 

 for them. Their signatures, written in the leaves, are plainly 

 outspread to view. The foliage of almost any oak tree or 

 hornbeam or clump of goldenrod will show in autumn the 

 characteristic marks of several kinds of them. 



Some of them make winding galleries like that of the 

 little fly in the aster leaf shown in figure 1, and when grown 

 leave the leaf through a slit in the epidermis and enter the 

 soil to undergo their transformations. Others excavate 

 broader chambers within the leaf, and remain inside them to 

 transform. The mothlet whose mine is shown in figure 2 

 is of the latter habit. It makes a broad mine in a lobe of a 

 leaf of the white oak. It disposes of its waste in a corner 



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