Until further experiments are made, it seems probable, then, that few if any insects have acute sight, that they see objects best when moving, and on the whole—except dragon-flies and other predaceous, swiftly flying insects, such as certain flies, wasps, and bees, which have very large rounded eyes—insects are guided mainly rather by the sense of smell than of sight. =Relation of sight to the color of eyes.=—It appears from the observations of Girschner that those Diptera with eyes of a uniform color see better than those with brightly banded or spotted eyes. Thus those flies (Asilidæ, Empidæ, Leptidæ, Dolichopidæ) whose predaceous habits requires good or quick sight have uniformly dark eyes, as have also such flies as live constantly on the wing, _i.e._, the holoptic Bombyliidæ, Syrphidæ, Pipunculidæ, etc., whose eyes are also very large. Those flies whose larvæ are parasitic on other animals have eyes of a uniform color that they may readily detect the most suitable host for their young; such are the Bombyliidæ, Conopidæ, Pipunculidæ, and Tachinidæ. Certain flies which live in the clear sunlight, as many Dolichopidæ, some Bombyliidæ, and certain Tabanidæ (Tabanus, Chrysops, Hæmatopota), and which are often easily caught with the hand, have eyes spotted or banded with bright or metallic colors. This is also a sexual trait, as the males of some horse-flies visiting flowers have eyes of a single color, the spots and bands surviving only on the lower and hinder parts of the eye, while their voracious blood-sucking females have the entire eye spotted or banded (Kolbe). =The color-sense of insects.=—Insects, as Spengel first suggested, appear to be able to distinguish the color of objects. Lubbock has experimentally proved that bees, wasps, and ants have this power, blue being the favorite color of the honey-bee, and violet of ants, which are sensitive to ultra-violet rays. It is well known that butterflies will descend from a position high in the air, mistaking white bits of paper for white flowers; while, as we have observed, white butterflies (Pieris) prefer white flowers, and yellow butterflies (Colias) appear to alight on yellow flowers in preference to white ones.