Page:Popular Science Monthly Volume 50.djvu/849

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—a laborer in the special field who produced results which fell at once into their proper order in his wider synthesis. As sculptors, they carved out shapely stones, from which he, as architect, built his majestic fabric. The total philosophic concept of evolution as a cosmical process—one and continuous, from nebula to man, from star to soul, from atom to society—we owe to Herbert Spencer himself, and to him alone, using as material the final results of innumerable preceding workers and thinkers.—Fortnightly Review.


By Prof. M. HEIM.

THE relations of ants with aphides and other insects have been studied by several authors, and constitute a field of interesting observation. The best known are those with the aphides and the cochineals, from which ants derive a food of honeydew. Where these do not abound, certain hemipterous insects take their place. Thus the caterpillar of the Lycæna is said to bear on its latter abdominal segments three or four pairs of projecting pimples with a central opening whence little drops of a special liquid exude under the caresses of Formica fusca. It is believed, further, that ants assist these insects in their molting by helping them get rid of their old skin. It seems to be established that ants protect some insects injurious to vegetation against the attacks of their enemies; in some cases, however, it is probable that they often take juice-sucking insects from young and tender parts to other, older parts of the plant, where they will do less harm, and thus in a measure protect the plant. Ants have been observed thus transporting aphides.

All insects producing nectar may be regarded, as a whole, as ambulatory nectaries. They are more powerful causes of attraction to ants than the extrafloral nectaries. Scattering themselves nearly all over the surface of the plant, they determine the coming and going of the ants, which indirectly protect the whole plant. Yet the damage done by the "ambulatory nectaries," which extract the nutritive juices from the plants and cause deformities in their organs, can hardly be said to be compensated by the incidental and uncertain protection which the ants may afford them in other respects.

The ants which are really protective to plants are not those which obtain their food (indirectly for the most part through the aphides) from the vegetable kingdom, but those which are really carnivorous. These are numerous in temperate climates, and their usefulness to agriculture and sylviculture is incontestable.