16 
conveying oxygen directly to the tissues. In the higher 
animals the blood is a carrier of oxygen, but the colourless blood 
of the insect is not a gas carrier, the oxygen being distributed 
directly through the tubes or “tracheae” to every part of the 
insect’s body. To ensure the free passage of air, each of the 
tiny tubes is provided with a spiral thread of “ chitin,” which 
acts like a coiled spring and prevents the tube from 
collapsing. One result of having such a multitude of air- 
tubes within its body is that the insect is extremely light 
and buoyant, so facilitating flight. This lightness is well 
exemplitied in the Pond-skaters, which can be seen on a 
summer day actually walking on the surface of the water 
in any clear pool. 
Wax. 
Wax is a secretion produced by eight glands situated on 
the under surface of the abdomen. Bees about to produce 
wax consume a quantity of honey and then hang in clusters 
motionless within the hive. After several hours the newly 
secreted wax oozes like oil from the glands and solidifies in 
eight little wax pockets. The little bits of wax so pro- 
duced are not unlike fish scales, and are frequently found 
in large numbers among the debris on the floor of the hive. 
The leaves of a bush on which a swarm has remained over- 
night are sometimes found glittering with newly made wax 
scales. When the bee is about to make comb it picks off the 
scales with its feet, carries them to its mouth, and works 
them up with its mandibles. The comb so produced is 
white—or almost white —although the wax scales are trans- 
parent. So snow is white while ice is transparent, and the 
explanation is the same in both cases. The snow and the 
honeycomb are full of little caves which reflect the light and 
produce the effect of whiteness. If the caves in a snowball 
be filled with water the whiteness disappears. 
Honeycomb. 
Honeycomb is one of the wonders of the world. It has 
extraordinary delicacy and beauty, and is so fragile that it 
ean hardly be touched without danger of breaking the cells, 
