Although in the foregoing chapter a little has been said on this subject,
there is a great deal more that a student should learn about the general
form of these creatures.
They begin life as white or nearly colourless grubs, which, after various
changes of skin, assume what is called the nymph or pupa stage, during
which a change occurs, believed to be peculiar to the _Hymenoptera_; the
fifth segment of the larval body is transferred to the mass which is called
the thorax, so that a portion of what looks like thorax is really the first
segment of the abdomen. Continental writers call this portion sometimes the
first abdominal segment and sometimes the median segment, but Newman gave
it a definite name, the "propodeum", and the most convenient method seems
to be to call it so, and treat it as a part of the thorax, calling the
first or basal segment of the abdomen {133} that which immediately follows
the regional constriction, which occurs between the propodeum and the
abdomen.
[Illustration]