ms larva, pupa and imago are fixed and
absolute. If we examine at a certain season the nest of a humble bee, we
shall find the occupants in every stage of growth from the egg to the
pupa, and even to the perfectly formed bee ready to break out of its
larval cell. So slight are the differences between the different stages
that it is difficult to say where the larval stage ends and the pupa
begins, so also where the pupal state ends and the imago begins. The
following figures (205-208) will show four of the most characteristic
stages of growth, but it should be remembered that there are
intermediate stages between. Now we have noticed similar stages in the
growth of a moth, though a portion of them are concealed beneath the
hard, dense chrysalis skin. The external differences between the larval
and pupal states are fixed for a large part of the year in most
butterflies and moths, though even in this respect there is every
possible variation, some moths or butterflies passing through their
transformations in a few weeks, others requiring several months, while
still others take a year, the majority of the moths living under ground
in the pupa state for eight or nine months. The stages of metamorphosis
in the Diptera are no more suddenly acquired than in the bee or
butterfly. In all these insects the rudiments of the wings, legs, and
even of the ovipositor of the adult exist in the young larva. We have
found somewhat similar intermediate stages in the metamorphoses of the
beetles. The insects we have mentioned are those with a "complete
metamorphosis." We have seen that even in them the term "complete" is a
relative and not absolute expression, and that the terms larva and pupa
are convenient designations for states varying in duration, and assumed
to fulfil certain ends of existence, and even then dependent on length
of seasons, variation in climate, and even on the locality. When we
descend to the insects with an "incomplete" metamorphosis, as in the May
fly, we find that, as in the case of Chloeon, Sir John Lubbock has
described twenty-one stages of existence, and let him who can say where
the larval ends and the pupal or imaginal stages begin. So in a stronger
sense with the grasshopper and cockroach. The adult state in these
insects is attained after a number of moults of the skin, during each of
which the insect gradually draws nearer to the final winged form. But
even the so-called pupae, or half winged individuals know