6 Introductory. 



minating Black-bug on the coffee trees. This is now known to be 

 quite a mistaken idea. The ants are attracted by a viscid, sugary 

 liquid emitted by the bugs, and which is, in fact, their excreta. 

 This substance is being constantly shed upon the surrounding 

 leaves, and proves very attractive, not only to ants, but to flies of 

 all kinds, and even to bees and wasps. It is of the same nature as 

 the ' honey-dew,' so abundantly produced by Aphides. Far from 

 feeding upon the bugs, I believe the ants actually transport them 

 from place to place to found fresh colonies of them in convenient 

 situations. It is certain that the small black nest-building ant 

 {Creinastogaster dokrni\ that is such a nuisance on some of our 

 estates, invariably includes in its nests colonies of Mealy-bugs 

 {Dactytopius) and one or more species of Lecaniuni. 



Amongst vertebrate animals birds are sometimes supposed to 

 play an important part in the warfare against Scale Insects ; but I 

 am inclined to think that their usefulness against this particular 

 class of insect pests has been overrated. I have watched many of 

 our insectivorous birds in Ceylon, and I have never found them 

 attracted by the plentiful supply of insect food spread before them 

 in a field of 'buggy' coffee. There is a peculiar aroma about many 

 of the Coccidse that is possibly distasteful to birds. 



Where Scale-bugs are present in large numbers, the leaves of 

 the tree or plant will usually be disfigured by a sooty deposit, the 

 nature of which has been frequently misunderstood by planters 

 many of whom look upon this as the active injurious principle, 

 instead of the mere outward indication of a less conspicuous 

 disease. To the best of my belief, this ' black fungus ' is itself 

 absolutely innoxious to the plant. It, in fact, germinates and 

 subsists upon the sweet liquid or honey-dew described above. In 

 dry weather the black growth can be easily peeled off in a thin 

 film, leaving the surface of the leaf healthy and unaltered in ap- 

 pearance, proving that the action of the fungus is quite superficial. 

 The supposed injury said to be due to the choking up of the 

 breathing pores (stomata) of the leaf, is largely illusory as the 

 greater number of these stomata are found on their U7ider surface, 

 where the fungus never occurs, owing to the simple fact that the 

 honey-dew can fall only upon the upper or exposed surface of the 

 leaves. Nietner {TJie Coffee Tree and its Enemies, p. 8) mentions 

 that two distinct species of the fungus have been identified from 

 Ceylon, named respectively, Syitcladiiini Nietneri, Rabenhorst, and 

 Triposporiini gardneri, Berkeley, both of them very similar in 



