Use of Honey-Secreting Glands 175 
number of scale-insects had established themselves on the 
stems, and that the ants had in a great measure transferred 
their attentions to them. An ant would stand over a scale- 
insect and stroke it alternately on each side with its antenne, 
whereupon every now and then a clear drop of honey would 
exude from a pore on the back of the latter and be imbibed 
by the ant. Here it was clear that the scale-insect was com- 
peting successfully with the leaves and sepals for the attend- 
ance and protection of the ants, and was successful either 
through the fluid it furnished being more attractive or more 
abundant.t I have, from these facts, been led to the con- 
clusion that the use of honey-secreting glands in plants is to 
attract insects that will protect the flower-buds and leaves 
from being injured by herbivorous insects and mammals, 
but I do not mean to infer that this is the use of all glands, 
for many of the small appendicular bodies, called “ glands ” 
by botanists, do not secrete honey. The common dog-rose 
of England is furnished with glands on the stipules, and in 
other species they are more numerous, until in the wild Rosa 
villosa of the northern counties the leaves are thickly edged, 
and the fruit and sepals covered with stalked glands. I have 
only observed the wild roses in the north of England, and 
there I have never seen insects attending the glands. These 
glands, however, do not secrete honey, but a dark, resinous, 
sticky liquid, that probably is useful by being distasteful to 
both insects and mammals. 
If the facts I have described are sufficient to show that 
some plants are benefited by supplying ants with honey from 
glands on their leaves and flower-buds, I shall not have much 
difficulty in proving that many plant-lice, scale-insects, and 
leaf-hoppers, that also attract ants by furnishing them with 
honey-like food, are similarly benefited. The aphides are 
the principal ant-cows of Europe. In the tropics their place 
is taken in a great measure by species of Coccide and genera 
of Homoptera, such as Membracis and its allies. My pine- 
apples were greatly subject to the attacks of a small, soft- 
bodied, brown coccus, that was always guarded by a little, 
black, stinging ant (Solenopsis). This ant took great care of 
the scale-insects, and attacked savagely any one interfering 
1] have since observed ants attending scale-insects on a large plant 
of Passiflora macrocarpa in the palm-house at Kew. 
