324. 
I am aware, they have only been described in Corelhra and 
Mochlonyx; it was, therefore, of great interest to find an entirely 
new type in another larva. As in Corethra and Mochlonyzx, the 
bladders in Mansonia are transversally 
striped, a fact to which we must pay 
attention, because the bladders on the 
tracheal system of imagines are without 
transversal stripes, the walls being of a 
| homogenous appearance. 
I have tried to understand the mode 
of action of this peculiar tracheal-system, 
being, as far as I know, unique among the 
insects. Later on Prof. A.Krogh has been 
kind enough to read my manuscript and 
has discussed the problem with me. — 
Out from the very broad band-like tracheal 
trunks it can only be concluded that the 
larvæ must be able to” produce a very 
powerful respiration. This must probably 
be of great significance for the larva 
because the air in the plant, from a 
respiratorical point of view, is a very 
bad medium, by no means being rich 
on oxygen. This has been stated by 
Ege (1915 p. 183). The main result of 
his investigations is, "that the composition 
of the air in the intercellular spaces of 
different aquatic plants is very variable. 
The oxygen percentage is low, rarely 
NL higher than 10 %/o and can especially 
K ANN during winter sink to about 1—2 "Yo 
AN N and even still less." When we remember, 
that the larva probably not fixes itself 
to the plant until in September and prob- 
ably detaches itself in May, the animal living as imago or egg 
during the time May-September, it will be understood, that the 
larva is dependent on the plant-air especially at the season when 
the oxygen percentage is lowest. 
Fig. 37, The trachael system 
of the larva, 
