In the September number we considered flowers and their invited guests, that is the insects useful in carrying pollen. The very things which attract useful insects to flowers are attractive also to useless insects. For example, nectar in a flower seems just as desirable to an ant as to a butterfly, but the ant is a creeping insect and would be likely to lose the pollen in passing from one plant to another. If useless insects found free access to flowers and carried off their food supplies, the useful insects would soon stop visiting them. It is of great advantage to flowers, therefore, to have some means of warding off the creeping insects. It must not be understood that all plants are equally successful in this matter, or that any plant is always successful, but there are certain things which seem to hinder or discourage the approach of creeping insects to flowers.

Perhaps ants may be taken as the best illustration of the insects whose visits are discouraged by flowers. They are very much attracted to the food supplies in the flower, especially the nectar, and are among the most intelligent of insects, often overcoming the most serious obstacles. They will be considered in this paper, therefore, as the insects which are seeking the nectar and pollen of flowers without invitation. A charming little book upon this subject has been written by Kerner, and translated into English, under the title which appears at the head of this paper. It is in this book that the chief obstacles to such unwelcome guests as ants are clearly stated.

Hairs. — One of the most common obstacles to ants is a barrier of hair. For some reason, ants dislike to cross such a barrier. Travellers in tropical countries, where ants abound, tell us that a hair rope laid around a tent is a very effective barrier against the invasion of armies of ants.Hair is very commonly found upon plants, and it may be noticed that it is apt to increase in amount and prominence towards or within the flower cluster.

Sometimes the flowers themselves are hairy outside, and in the case of the trailing arbutus, whose flowers close to the ground are in special danger from creeping insects, the flowers are filled with a fluffy mass of hairs. In our illustrations, the wild columbine, the Oswego tea, the sunflower and the ox-eye daisy are all hairy plants and difficult for ants to climb. In the September number are illustrations of the mallow, the lady's slipper, and the New England aster, all of which are hairy and discouraging to ants.

An interesting fact in connection with the wild columbine may be noted. The nectar is deposited in the knob-like bottom of the long tubular spurs, and the entrance is so carefully guarded that only a long and slender proboscis, like that of a moth or a butterfly can reach the nectar. The bumblebees, however, have learned this fact, and bite through the tips of the spurs and steal the nectar. As a consequence, the wild columbine is said to be little visited by the proboscis-bearing insects, and its pollination is seriously interfered with.

Sticky excretions. — Some plants have the power of excreting upon their surface a sticky substance like mucilage. This mucilage may be produced by hairs, which are then called "glandular hairs," or it may appear directly on the surface of the plant. When ants or other insects try to cross such a barrier they are not merely stopped but caught. Upon "glandular" plants it is very common to see small insects stuck fast, and it is more than probable that the nourishing material of their bodies is digested and absorbed by the plant. In this way the plant not merely stops the insect, but catches and devours it.

A very common illustration of such a plant is the "catchfly," whose name suggests its power. The joints of its stem are long, and near the upper end of each joint is a band of mucilage. This series of sticky bands forms a very effective barrier to any insect trying to crawl up the stem.