96 PLANTS AND ANIMALS 
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 thou- 
sand 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 (Noctuide) it is 
sometimes only eight millimetres (4 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 
