Some irregularities in the division of the tunnel into separate 
cells by means of transversal septae are, as means the author, caused by 
the influence of cold and rainy weather on the activity of Ceratina. 
The distribution of sexes in the nests of Ceratina callosa is not cor- 
responding to the law of the „protherothesis of the males“ (Verhoeff 
1891), as the lowest cells in them (the first constructed) are occupied 
by males. This exceptional fact seems to stand in connection with another 
unexpected phenomenon in the biology of the Ceratina, namely, their 
fertilization takes place but after they have begun to work at their nests, 
which phenomenon has many a time been observed by the author. 
Ceratina callosa but seldom closes its nest with a special stopple. 
This latter is constructed with coarse pieces of pith and is about 1,5—2 cm. 
thick; its superior side is inserted at short distance (about 1 cm.) from 
the entrance into the nest. 
Fully developed Ceratinae begin to leave the cells in about the 
middle of July, but sometimes not before the end of July, or the first 
days of August. 
During this process the young Ceratinae, developing before the 
others in the cells nearest to the bottom of the nest, force their way to 
the uppermost parts of the latter, passing by those, who are not yet ready 
to come out (larvae and pupae, sometimes of all ages). 
A successful result of such an extraordinary way of leaving the cells 
is reached thanks to the width of the canal and the presence of the double 
septae in it. The uncommon width of the canal allows the young Cera- 
tinae to pass easily by the undeveloped ones. The cavities of the double 
septae also may serve as reserves of free space, though not in transversal 
direction, as in the preceding case, but in a longitudinal one. ‘And preci- 
sely thanks to these, receptacles for the fragments of the transversal sep- 
tae, demolished by the young Ceratinae forcing their way out, are formed 
in the canal. The larvae and pupae contribute, in addition to this, by their 
movements to the clearing of the surrounding parts of the canal from the 
above mentioned fragments. 
In this way, after the ascending of the sooner developed bees from 
the bottom of the nest to its top, free spaces in the canal are secured, 
where the remaining ones are continuing their development. Into the 
cavities of the double septae the author placed larvae and pupae of Cera- 
fina callosa, extracted from other nests. In such cases, after the passage 
of the first young Ceratinae to the uppermost part of the nest, the others 
were usually found mutilated or dead. 
In the second half of July Ceratina callosa usually leaves off buil- 
ding cells in its nest, but sometimes this happens but in the first weeks ot 
August. If Ceratina suspends its work not long before the passing of the 
young ones to the upper part of the nest has begun, then its does nof 
shut the last cell with a fence, but remains itself near the entrance of 
the cell, defending it from ants, earwigs etc. (pl. Ш, fig. 9). 
