As regards the kinds of insects which visit flowers for food, these are very numerous and belong to almost every section of that large class. In many, such as Neuroptera, Orthoptera, Hemiptera, Coleoptera, there is very little special adaptation for their flower-feeding habits, and these insects visit flowers, such as the _Umbelliferæ_, in which the nectar and pollen are freely exposed, and lie open to all. Many of the Diptera, or Flies, are in the same case; but in some families, such as the _Bombyliidæ_, high specialization for securing food from flowers is found: the creatures are provided with elongated probosces for sucking nectar even when it is deeply hidden, and no other food is used by the insects in their adult stage. But it is among the long-tongued Bees and the Lepidoptera (Butterflies and Moths) that the highest degree of adaptation in this direction is found; and the modifications are associated with those flowers which have become most highly specialized for insect pollination, and most completely dependent on it. In the Bees the legs have become much modified for the gathering of pollen, and the mouth is a long flexible sucking-tube which when not in use is carried rolled up in a spiral. The pollen, on which food alone the young bees are fed, is gathered and stored among rows of hairs on the legs, and in the more highly specialized forms it is wetted with honey so as to form a compact mass, easily carried and easily removed when the nest is reached. The balls of pollen thus formed are sometimes nearly the size of the body of the bee, and may contain one to two hundred thousand grains of pollen. The formation of the mouth is beautiful and complicated, adapted to the rapid sucking up of nectar even if deeply placed in the flower. The nectar is stored in the body of the bee, and subsequently transferred to the waxen honey-cells in the hive. In the Butterflies and Moths the mouth parts are also modified for sucking, and as these insects do not build nests or take care of their offspring as Bees do the mouth is formed solely for the purpose of securing the nectar which is their only food. The proboscis varies greatly in length in different groups, according to the kind of flower which they visit. In the Owl Moths (_Noctuidæ_) it is sometimes only eight millimetres (1/3 inch) long; in many of the Butterflies it is about half an inch. In the Hawk-moths it attains a remarkable development, necessitated no doubt by the habit of these insects of not alighting on or entering a flower, but hovering in front of it as a Humming Bird does, and sucking up the nectar while thus poised. The proboscis of the Convolvulus Hawk-moth measures 65 to 80 millimetres (2-1/2 to 3-1/4 inches), and some of the Tropical allies of this moth have probosces twice or even three times that length. These species feed on the nectar of flowers with tubular corolla of corresponding dimensions. Most of the Hawk-moths