320 DIPTERA. 
face of the water ; but they are too mi- 
nute to be observed^ without the assist- 
ance of a good microscope. When the 
time for transformation is come^ these 
larvae creep out of the water, and having 
found a suitable place, they remain at 
rest for a short time : the body be- 
comes thicker, the tail shrinks, and the 
whole skin assumes a shell-like hardness. 
Lucy, The old skin, I suppose, an- 
swers for the case, within which they 
make their change ? 
Mother, Yes, it does ; and some sin- 
gular alterations then take place. The 
head loses its former shape, and the rudi- 
ments, or beginnings, of two pair of horns, 
are seen to burst through the old skin ; the 
lower pair, with a slight bend, project 
nearly forward ; while the upper pair first 
rise upward, and then gradually curve 
downward. 
Lucy, What use can a chrysalis make 
of horns, for as it cannot move it cannot 
defend itself? 
