EXTENT OF LEAF-MINING HABIT 



39 



found on ferns. Excepting attacks by the Diptera, herbs 

 have in general fewer leaf -miners than have shrubs and 

 trees. 



Sometimes a genus, or the species of a natural division of 

 a genus, will show a preference for closely related plants. 

 Thus the caterpillars of the genus Aphelosetia all mine the 

 leaves of grasses and sedges, and those of Mompha and 

 Laverna show a marked preference for members of the 

 evening primrose family, especially for Oenothera and 



Fig. 17. A leaf of walking-fern (Camptosorus) bearing two mines, one 

 with a fixed puparium protruding. 



Epilobium. The beetle grubs of the genus Phyllotreta 

 mine the leaves of crucifers. The food plants of some one 

 hundred and eighty species of Lithocolletis are known. 

 Nearly all of these are found on trees and shrubs of the 

 amentiferous groups, forty -four being attached to the genus 

 of oaks (Quercus) alone. 



The plants attacked by any one species of miner usually 

 are of one species or of a group of nearly related species. 



