620 D. KEILIN 
assuming that the adult flies which he examined were derived 
from normal larvae devoid of calcospherites. Personally, 
I have found that in all Diptera, the larvae of which contain 
stored calcium carbonate, this substance disappears during 
the pupal phase, and the adult flies are completely devoid 
of this product of excretion. I must say, however, that the 
disappearance of the calcium carbonate seems to be a more 
complicated process than that suggested by Pantel (17, 1914). 
In the case of the Ptychoptera larva, where calcium car- 
bonate, in form of a thick suspension of small granules, is 
enclosed in the distended portion of the Malpighian tubes, 
it is possible that the milky contents of these tubes are emptied 
into the hind-gut and are thus expelled from the body. It is, 
however, difficult or even impossible to suppose that the large 
calcospherites can follow the same channel in the larva 
of Acidia heraclei, for the Malpighian tubes of this 
larva, as in other Dipterous larvae, are completely devoid of 
peristaltic movement. 
In the case of the Acidia larva and the larvae of Agromy- 
zinae, which attack Cirsium lanceolatum, I was able 
to follow, step by step, the disappearance of the calcospherites 
during the metamorphosis of these insects. Hach of these 
larvae, as is the case in all the Cyclorhaphous Diptera, trans- 
forms into a pupa which remains enclosed in the puparium 
formed by the contracted and hardened last larval cuticle. 
During the first day of the metamorphosis the calcospherites 
of these larvae can be easily seen either by transparency or 
by dissection. When the pupa is completely formed and 
separated from the last larval cuticle or puparium it loses its 
ealcospherites, which are gradually dissolved. At the same 
time the puparium becomes very brittle and presents a white 
opaque ‘fossilized’ appearance. After the emergence of the 
adults the empty puparia become so fragile that it is difficult 
to detach them from the plant, for they pulverize under the 
slightest pressure. On treating such an empty puparium with 
dilute hydrochloric acid a very active effervescence takes 
place, with the evolution of carbon dioxide, and all that 
