Leaf-cutting Ants Lyi 
provided with a wonderful mechanism, by means of which 
its pollen is rubbed into the head of the bee, and received on 
the stigma of the next plant visited There are many 
humble-bees, of different species from ours, in tropical 
America; but none of them frequented the flowers of the 
scarlet runner, and to that circumstance we may safely ascribe 
its sterility. An analogous case has been long known. The 
vanilla plant (Vanilla planifolia) has been introduced from 
tropical America into India, but though it grows well, and 
flowers, it never fruits without artificial aid. It is the same 
in the hothouses of Europe. Dr. Morren, of Liége, has 
shown that, if artificially fertilised, every flower will produce 
fruit; and ascribes its sterility to the absence, in Europe and 
India, of some insect that in America carries the pollen from 
one flower to another.?, When those interested in the accli- 
mature of the natural productions of one country on the soil 
of some distant one, study the mutual relations of plants and 
animals, they will find that in the case of many plants it is 
important that the insects specially adapted for the fertilisa- 
tion of their flowers should be introduced with them. Thus, 
if the insect or bird that assists in the fertilisation of the 
vanilla could be introduced into and would live in India, the 
growers of that plant would be relieved of much trouble, 
and it might be thoroughly naturalised. Judging from my 
experience, it would be useless to attempt the acclimature 
of the scarlet-runner bean in Chontales unless the humble-bee 
were also introduced. 
Caterpillars, plant-lice, bugs, and insect pests of all kinds 
were numerous, and did much harm to my garden; but the 
greatest plague of all were the leaf-cutting ants, and I had 
to wage a continual warfare against them. During this 
contest I gained much information regarding their habits, 
and was successful in checking their ravages, and I shall 
occupy the remainder of this chapter with an account of them. 
LEAF-cuTTING Ants.—Nearly all travellers in tropical 
America have described the ravages of the leaf-cutting ants 
(Zcodoma) ; their crowded, well-worn paths through the 
1 Gardener’s Chronicle, October 24, 1857, and November 14, 1858; 
also T. H. Farrer, in Aunals of Natural History, October 1868. 
2 Taylor’s Annals of Natural History, vol. iil. p. I. 
