40 NOTES ON 
their bodies becoming specifically heavier, they 
descend. The contemplation of contrivances 
such as this, so admirably calculated to effect 
their intended end, must surely elicit the highest 
admiration of the works of the Creator, even 
from the most obtuse and thoughtless. Many 
fish possess an air-vessel, which, through the 
aid of proper muscles, they have the power of 
compressing or dilating, to facilitate their ascent 
and descent. In these insects the same pur- 
pose is effected by the simple law of capillary 
attraction only. 
Both in the larva and perfect state this insect 
feeds on the eggs and small aquatic larva of 
insects, and the thoughtless victim is often 
captured in descending to the bottom of its 
element, by the wary position in which its 
destroyer places itself, with its rostrum up- 
wards, ready to commence an attack. The 
eggs are their favourite food; these they devour 
with avidity, as soon as they are emitted by the 
parent, even before they reach the bottom of 
the water. 
The species belonging to this family (Noto- 
nectide) are numerous, and most of them are 
inferior in interest, as microscopic objects, to 
the one here figured. Dr. Leach has separated 
