201 
The dates, on which the moults were gathered are also noted in 
the list before. 
4. Infection by Tyroglyphus farinae. 
Tyroglyphus farinae is a small mite strongly flattened dorsoventrally, 
about 0.4 millimetres long. The eggs of this mite seem always to 
be present in meal or bran, to develop only under definite circum- 
stances, of which moisture seems to be the most important factor. 
If the conditions of life are favourable to this mite, the multipli- 
cation may be so enormous that the whole layer of bran or meal 
seems to have changed into a homogeneous mass of Tyroglyphus. 
It is true that this mite does not infest the larva, still the growth 
of the larvae is considerably injured by the withdrawal of food. The 
development of the pupae gathered from a jar infected with Tyro- 
glyphus, also suffers great disturbances by this mite. 
In close little heaps it nestles between and behind the legs, wings 
and antennae, and causes deformities of these organs in the later 
emerging beetles. 
The researches with respect to Tenebrio were started in the spring 
of 1915 and continued without any incubators throughout the summer. 
The mite first made its appearance in 6 cultures at the same time, 
and that in jars which had been purposely placed in very damp 
surroundings; the development and multiplication of the mite in these 
jars was so intense that these cultures had to be done away with. 
Later on a similar experience was made with several other cultures 
standing free in the laboratory, when a spell of humid weather 
came. At first there seemed to be no better means than insulating 
these vessels from the rest. The necessity of this insulation to prevent 
all the cultures from being infected within a short time, is apparent 
from the fact that the infection passes from one jar to another in 
spite of their being covered with a glass plate, lying directly on the 
rim. The mite crawls up the wall of the glass, and tries to get out 
between the rim and the covering glass plate in which it generally 
succeeds, as there is always an interstice wide enough to allow its 
flat body to pass through. 
Then an expedient was tried, which was efficacious so far as to 
prevent an infection from passing from vessel to vessel, even if 
they stand uncovered side by side. 
At about 2 centimeters below the rim a ring of vaseline was 
applied inside. 
Through this greasy substance the mite cannot get and the infection 
