Not all bats feed on insects. Some such as the Pallas' long-tongued bat (Glossophagasoricina) have discovered that nectar is very nutritious, and have refined their flying skills so that they can hover in front of flowers, just like humming birds, and gather nectar by probing deep into the blossoms with long thin tongues. Just as a great number of plants have evolved to exploit the services of insects as pollinators, so too some rely on bats. Some cacti, for example, only open their blossoms at night. These are large, robust and light-coloured, for in the darkness colour is valueless. Their scent, however, is heavy and strong and the petals project well above the armoury of spines on the stems so that the bats are able to visit without damaging their wing membranes.
The biggest of all bats live only on fruit. They are called flying foxes (e.g. Pteropus giganteus), not only because of their size and some of them have a wing span of one and a half metres but because their coats are reddish brown and their faces are fox like. They have large eyes but only small ears and lack any kind of nose protrusions and they are not equipped with any form of echolocation apparatus. Whether this major difference between them and other insectivorousbats indicates that the two groups derive from separate branches of primitive insectivores is not yet agreed. Unlike insectivorousbats, fruit bats do not live in caves but in the tops of trees in large communal roosts. In the evening, they set of in parties to feed. Their silhouette is quite unlike that of birds, for they lack a projecting tail and their flight is very different from the fluttering of insect hunting bats. Their huge wings beat steadily as long skeins of them keep a level purposeful course across the evening sky. They may travel as far as 70 kilometres in their search for fruit.