208 
with the larvae) profited by this addition, but, of course, not the 
pupae that had been then collected already. Hence the pupae-mor- 
tality of 1916/1917 is still very high and even higher than of 
1915/1916. Now, the connection (alluded to above) that may exist 
between the mortality figures of larvae and pupae appears from the 
following. When one allows a number of counted larvae to pupate 
in a glass jar, and after some time adds the pupae gathered + 
the dead larvae + the remaining living larvae, the sum total is, as 
a rule, smaller than the number of larvae with which the culture 
was started. As an escaping of larvae from the glass jars does not 
occur (we never found any larvae crawling about in the incubator 
since the use of glass jars), the lacking larvae cannot but have been 
eaten up. This eating-up most probably took place not in the larval 
but in the pupal state, when the newly emerged body is still soft. 
The annihilation of these still soft pupae has then been executed in 
a much more radical manner than in the larvae gnawed at, while 
by the white colour the fragments of these pupae are much more 
difficult to find back than the relatively bigger remains of the brown 
larval bodies. This practically estimates the mortality figure of the 
larvae too high, and that of the pupae too low. This circumstance 
applies more specially to the year 1915/1916 than to 1916/1917, 
because in the latter year, as has been mentioned, a part of the 
larvae were already provided with slices of potato. 
This expedient promoted the growth of the larvae and an earlier 
pupation, and strongly diminished the mutilation of the pupae; in 
consequence the figure of the larvae mortality (by the manner of 
fixing this figure) had then to decrease. 
Now although these influences have, no doubt, asserted themselves, 
they were not of such a nature as to satisfactorily account for the 
great difference of the larvae mortality in these two years. Similar 
great differences appear also between the cultures (of one series) 
that have been exposed to equal exterior influences of food and 
temperature, and disagree only in one point, viz. in the time when 
the eggs were deposited, and in the number of these. 
c. The mortality among the pupae. 
The mortality among the pupae appears in the same way as among 
the larvae, viz. by gnawing-off, and by an unknown cause by which 
they dry up or, by way of rare exception, become black, and the 
body remains soft. 
Besides these pupae eaten at, also others are found, not dead but 
wounded. The humour that has flowed from the wound is then 
ment ee ag wi, Rae 
