302 THE AMERICAN MONTHLY [Nov 
is dilated and the food ascends at the same moment to 
fill the vacuum produced, thus passing to the mouth and 
stomach, being further assisted thereto by the muscles 
of the proboscis.—Mrs, W. Major. 
The function ascribed above to the trachea is a novel 
one, and it is difficult to understand how a vacuum can be 
produced in the csophagus and its connections by driv- 
ing the air out of them, even if it were possible. In in- 
sects the mouth can only be considered as connected with 
respiration in the most indirect manner, if at all; for al- 
though in certain acari the air-tubes open at the base of 
the mouth, there seems to be nothing analogous in in- 
sects. Respiration in insects is effected by means of two 
large canals, called “ tracheaw,’’ running along the sides of 
the body underneath the outer surface, which communi- 
cate with the air by short tubes called spiracles situate 
along the sides. I take it that these tubes can never be 
exhausted of the air they contain, seeing the walls are 
supported by spirally convoluted fibres, which impart 
great strength and prevent collapse; and that the air is 
changed within them, according to the necessity of the 
creature, by the closing or opening of the spiracles and 
the continuous rhythmic movement of the body. It may 
be well to say a few words with respect to the means by 
which in the Proboscidea the food is drawn up into the 
stomach. The Hymenoptera,the Lepidoptera, and Diptera — 
are provided with a bladder-shaped distension of the ceso- 
phagus which would appear to be a modification of the 
crop, and is called a ‘“‘sucking stomach.’’ This is not a 
receptacle for food, but by its distension and the conse- 
quent rarefaction of the air contained therein it promotes 
suction of the same and facilitates the rising of fluids in 
the proboscis and the csophagus, and it is by this means 
these insects rifle the flowers of their contents.—JZ. Bos- 
tock. 
