618 D. KEILIN 
A question now arises: What becomes of the stored calcium 
carbonate during the ultimate stages of the life of the insect ? 
TEXT-FIG. 4. 
Acidia heraclei. I. a.m., anterior pair of the Malpighian 
tubes; c., terminal portion filled with the calcospherites ; 
g., gut; p.m., posterior pair of Malpighian tubes. II. portion 
of the anterior pair of Malpighian tubes showing the calcospherites 
free in the lumen of the tube. 
According to Pantel (17, 1914) the calcium carbonate of 
the Ptychoptera larva disappears before the metamor- 
phosis takes place. He considered that it does not dissolve 
