RAVAGES OF THE LEAF-MINER. 35 



tated trees. On otherwise healthy trees the leaves attacked by the 

 miner do not appear to be injured except at the spot where the tissue 

 has been eaten away, but on those already weakened by adverse cir- 

 cumstances the leaves fall rapidly, leaving the branches quite bare 

 except for a few young leaves at the tips, and these seemed to fall 

 before they reached full size. 



At Quebrada Arenas, between Caguas and Cayey, the writer found 

 a coffee farm occupying the sides of a ravine running east and west. 

 Large trees which must have furnished heavy shade had fallen, doubt- 

 less at the time of the hurricane, leaving the coffee exposed. On the 

 north side of the ravine the trees had nearly all lost a large proportion 

 of their leaves and most of those which remained were of a noticeably 

 lighter yellowish color. With few exceptions they showed the work 

 of the leaf- miner, and most of them were undersized or deformed, 

 indicating that the insect had begun its attack before the leaves had 

 been fully expanded. That the leaves fell solely on account of the 

 ravages of the miner seems, however, improbable in view of the 

 obvious debility of the trees from other causes; but it seems entirely 

 probable that the insect was hastening the deterioration of this part 

 of the plantation. A sufficient cause of the unhealthy condition of 

 the trees existed, however, in the fact that the ground under the 

 exposed trees was covered with a dense growth of grass, to say noth- 

 ing of the possibility of the direct injury by the sun on the thin bark 

 of the slender and fully exposed trunks and branches of the spindling 

 trees. 



On the south side of the ravine where most of the shade trees were 

 still standing the coffee leaves had preserved a more healthy, dark- 

 green color, and, while the leaf -miner was also frequent, it seemed to 

 make less progress and many of the leaves were uninjured. While 

 the contrast in this case was very marked and might on superficial 

 inspection appear to have warranted the opinion that the difference in 

 exposure determines the severity of the leaf -miner and the resulting 

 unhealthfulness of the coffee, this view seems to be negatived by the 

 fact that similarly ill-conditioned trees showed the lighter color and 

 lost their leaves, though perhaps with less rapidity, in places where 

 there were few, if any, leaf -miners, but where the ground was covered 

 with grass or where drainage was obviously defective. These facts 

 appear to warrant the conclusion that an unhealthf ul condition which 

 gives the coffee leaves a yellowish color also invites the attacks of the 

 coffee miner. This opinion seemed to be further justified by many 

 instances where the removal of the shade trees had worked no appre- 

 ciable damage when the foliage of the coffee was thick enough to pro- 

 tect the trunks and keep the grass from growing underneath. Special 

 notice was also taken of trees which through some accident or neglect 

 had been allowed to grow up in exposed places, Where the conditions 



