as Walsh observed, are converted
in the male into simple clasping organs. And to omit a number of
instances, in the suctorial Hemiptera or bugs we have different grades
of structure in the mouth-parts. In the biting lice (Mallophaga) the
mouth is mandibulate; in the Thrips it is mandibulate, the jaws being
free, and the maxillae bearing palpi, while the Pediculi are suctorial,
and the true bugs are eminently so. But in the bed bug it is easy to see
that the beak is made up of the two pairs of jaws, which are simply
elongated and adapted for piercing and sucking. Among the so-called
haustellate insects the mouth-parts vary so much in different groups,
and such different organs separately or combined perform the function of
sucking, that the term haustellate loses its significance and even
misleads the student. For example, in the house fly the tongue (Fig. 210
_l_, the mandibles, _m_, and maxillae, _mp_, are useless), a fleshy
prolongation of the labium or second maxillae, is the sucker, while the
mandibles and maxillae are used as lancets by the horse fly (Fig. 211,
_m_, mandibles, _mx_, maxillae). The maxillae in the butterfly are united
to form the sucking tube, while in the bee the end of the labium (Fig.
212) is specially adapted for lapping, not sucking, the nectar of
flowers. But even in the butterfly, or more especially the moth, there
is a good deal of misapprehension about the structure of the so-called
"tongue." The mouth-parts of the caterpillar exist in the moth. The
mandibles of the caterpillar occur in the head of the moth as two small
tubercles (Fig. 213, _m_). They are aborted in the adult. While the
maxillae are as a rule greatly developed in the moth, in the caterpillar
they are minute and almost useless. The labium or second maxillae, so
large in the moth, serves simply as a spinneret in the caterpillar. But
we find a great amount of variation in the tongue or sucker of moths,
and in the silk moths the maxillae are rudimentary, and there is no
tongue, these organs being but little more developed than in the
caterpillar. Figure 213, B, shows the minute blade-like maxilla of the
magnificent Luna moth, an approximation to the originally blade-like
form in beetles and Neuroptera. The maxillae in this insect are minute,
rudimentary, and of no service to the creature, which does not take
food. In other moths of the same family we have found the maxillae
longer, and touching at their tips, though too widely s