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Rn eo eos ae lle tte 
1914] Longevity of Insects 347 
ecdysis is an extra excretory process. Quaintance and Brues 
(42) found that highly nutritive foods caused less molts but 
insufficient and disagreeable food resulted in more molts. 
Sharp says that many hibernating larve have an extra 
molt. This may be either a sign of over-feeding or of feeding 
on some less nutritive substance in larger quantities. 
I found in my first experiments with Codling moth larve 
in windfall apples that those larvze which were about to hi- 
bernate remained inactive in the apple for some time (two days 
to a week) without eating before leaving the fruit to form a 
cocoon. 
If it is granted that there is a condition of over-feeding 
in the larve before hibernating, it will be seen that there are 
many similarities between this stage and the condition before 
and during the molt. Before the molt, there is a period of 
great feeding—then a short period of quiescence, then the his- 
tolysis begins. 
The process of histolysis is one of rejuvenation—in the 
second part of this paper, a résumé of the present day knowledge 
of the process of senescence was given—the most up-to-date and 
I think the best of these theories is the one advanced by Child. 
Child, basing his theory on the alveolar nature of protoplasm 
and on the nature of the metabolic processes and their tendency 
to lead to structural differentiation in the establishment of 
cytoplasmic alveolar walls, formulates the following law: 
‘Senescence in nature consists physiologically in a decrease in 
the rate of metabolism and this is determined morphologically 
by the accumulation in the cell of structural obstacles to 
metabolism, e. g., decrease in the permeability, increase in 
density, accumulation of relatively inactive substances, etc. 
Rejuvenescence consists physiologically in an increase in the 
rate of metabolism and is brought about in nature by the re- 
moval in one way or another of the structural obstacles to 
metabolism.’’ Since in the process of pupation, the tissues pass 
through a more or less complete process of histolysis which is 
aided by phagocytes, and new tissues often arising from germ- 
inal buds absorb this old material (Sharp, Packard (41) 
and Ganin (18), the cells of these tissues are probably less com- 
plex in their cytoplasm. Sharp says that the physiological con- 
ditions of the later larval life are different from those of the earlier 
