If the insect have a suflSbcient supply of food, it only
continues for a few weeks in the larva state, when it ra-
pidly change^ to the pupa, shewn in the drawing, fig. 2.
When it is desirable to preserve it for the microscope,

• Vol 6, Sup. Plate 66, fig. 4, D,



54 MICROSCOPIC ILLUSTItATIONS.
this change may be retarded by keeping it in clear spring
or river water. The former seldom offers sustenance to
animalcules, and therefore effects this object ; which is
often very desirable, on account of the scarcity of this
species.
The transformation of this animal from the larva to the
pupa is one of the most singular and wonderful changes
that can be conceived; and, under the microscope, pre-
sents to the admirer of nature a most curious and inte-
resting spectacle. Although the whole operation be
under the immediate inspection of the observer, yet so
complete is the change, that its former organization can
scarcely be recognized in its new state of existence.
