220) PSYCHE. 
of a fleshy cone. An interesting feature 
of this arrangement is that the trachea 
seems in Psocus (proper) to enter the 
pterostigma-sac after the spindle-shaped 
bladder. We find sometimes that the 
end of the trachea does not follow strictly 
the lower and the external margin of the 
pterostigma, and such occurrences are 
marked in the description, the ‘‘ ptero- 
stigma somewhat exceeds the vein below 
and externally,” whereas it exceeds not 
the vein but only the trachea. 
4. The lock of the fore-wings. 
It is well known that lepidoptera, hy- 
menoptera, orthoptera, and phryganina 
possess an arrangement on the hind mar- 
gin of the fore wings to clasp the front 
margin of the hind wings during flight. 
Thus both wings work exactly together 
as if there was only one wing on each 
side. This arrangement — which I call 
the lock —is of very different shape and 
form, and is nowhere mentioned as 
existing in the family of psocina. As 
far as my observations go, it is to be 
found in every four-winged genus, just 
where the anal vein is united to the hind 
margin. Descriptions of the species 
remark frequently a dark or black spot 
in this place, which spot covers the lock. 
The parts are here, as they are in the 
pterostigma-hook, more strongly chiti- 
nous, and as everywhere, in consequence 
of stronger action impending upon those 
parts, darker colored. The anal] vein is 
an exception, compared with other veins, 
because it is not accompanied by any 
blood vessel; at least I have not been 
able to discover one even in the newly 
transformed imago. 
anal vein has always an aspect different 
from all others; it looks clear and as if 
Furthermore the - 
something present on the other veins 
was wanting here. But there is another 
remarkable difference. As said before, 
all the other veins form a double net of 
tracheae, one belonging to the upper 
membrane of the wing, the other to the 
under membrane ; both exactly covering 
one another, and their veins forming a 
loop at the hind border of the wing. 
Now the anal vein belongs strictly to 
the under side of the wing, and, as it 
seems, only the branch belonging to the 
under membrane is developed, and this 
is provided with a spiral thread much 
stronger than in the other veins and pas- 
sing on each side considerably beyond 
the trachea, which has therefore more 
or less dentated margins. The anal vein 
of the upper membrane can not be entirely 
wanting, and I was able to observe that 
it forms a very small, perfectly hyaline 
vessel without any indication of a spiral 
thread, and that the trachea of the under 
membrane disembogues as a_ recurrent 
vessel in the axillary vein. The anal 
vein originates at the base of the wing 
from a large trachea passing through the 
posterior callus, and connects, beyond 
the basal articulation of the wing, with 
the trachea of the submediana and with 
those of the mediana through a strong 
loop. A straight, chitinous rod also 
connects the anal vein directly with the 
base of the median vein. By this in- 
genious arrangement the anal vein can 
be compared to a shroud, which strength- 
ens the wing and principally the point 
where both wings are to be connected 
during flight, by bringing them into de- 
pendence upon the stronger muscles 
which move the principal veins originating 
from the anterior callus of the wing. 
