211 
that the mutilating of the pupae by the larvae was perhaps brought 
about by want of humidity, given the circumstance that the food 
in the incubator dried up more and more, until it got crumbly and 
was renewed. 
I first put out a feeler by laying large thin slices of fresh beet- 
roots on the top of the food in a few jars. The outcome was a 
surprise. The harvest from these jars provided with slices of beet- 
root was not only greater, but the eating of pupae had diminished 
in a striking way. Then the following course was taken. 
Two jars were provided with fresh food. In each an equal quan- 
tity of larvae was put. One of these jars got 8 slices of beetroot 
or carrot, the other none. From these two jars 6 harvests of pupae 
were taken. The results are shown in the tabular scheme before 
and speak clearly enough. 
One will see a considerable decrease of the deathrate in each 
harvest. The decrease is slightest in the 2ed and the 5 harvest. 
Now it appears from notes made, that in the periods between 
January 10 and 17 and between Jan. 30 and Febr. 6 i.e. between 
the 1st and 2rd and the 4h and 5 harvests no carrot had been 
added, because the bran still felt very humid to the touch from the 
previous time. 
This after-effect of the humidity of the previous addition of slices 
is yet so great as to diminish the deathrate in both cases, in the 
AED /,, in the 2ad by 25 °/,. 
This experiment was repeated on another quantity of larvae, of 
which in the two jars an equal number was again deposited. Here, 
too, the result was again in favour of the jar with slices, of which 
the mortality was 20°/, less than in that without carrot (of Experi- 
ment IJ). It is also remarkable that in both experiments the total 
number of gathered pupae is larger, which clearly indicates that 
the growth of the larvae is very much furthered by the humidity. 
I was not quite convinced and started a third trial. 
I then reversed the state of humidity for the larvae at every turn 
after a number of harvests. Two jars were each provided with 
exactly 1000 larvae. In order to be sure that these larvae were in 
the same stage of development, they were weighed beforehand. The 
weights were the same for each group, viz. 110 grammes. The 
vessels got the same weight of food; one of them got 8 slices be- 
sides, the other none. 
When the food in the jar with slices was consumed earlier than 
that in the other (which always occurred in all series of experi- 
