The Life Processes of the Individual 153 
in respiration have been described by Carlet, 1 who dis¬ 
tinguishes seven sets. It is stated by Djathchenko 2 that in 
expiration the spiracles are momentarily closed, the contrac¬ 
tion of the muscles thus forcing air to the minute branches. 
The spiracles are then opened and the air is expelled. 
EXCRETION 
The products of the breaking down of protoplasm consist, 
as previously stated, of carbon dioxid, water and various 
compounds containing nitrogen. Since the adult honeybee 
can live for long periods (especially in winter) on pure sugar, 
excretion must at times be reduced to a minimum. Sugar 
breaks down into carbon dioxid and water, both of which 
may pass off as gases through the tracheal system. It is 
only the other components of honey and the pollen which 
ultimately go to form nitrogenous compounds. The carbon 
dioxid is all expelled through the tracheae and probably 
most of the water escapes as vapor by this course, although 
some may be ejected with the nitrogenous compounds. 
The excretory organs are the Malpighian tubules (Fig. 60, 
Mai), about 100 in number in the bee, which open into the 
alimentary canal at the junction of the ventriculus and the 
intestine. They are long delicate tubes which coil about 
the other viscera. These tubules are only one cell in thick¬ 
ness and the ends of these cells ( Epth , Fig. 77, C) often 
bulge into the cavity of the tubule. The junction of the 
Malpighian tubules with the intestine is shown in Fig. 77, G. 
Minute crystals of urates have been found in the Malpighian 
tubules. The excreted products empty into the intestine 
and are expelled in the feces. 
In the fat body (located in the body cavity) are found 
certain large cells of rather mysterious function, called 
1 Carlet, G., 1884. Sur les muscles de [’abdomen de l’abeille. Comptes 
rendues de l’Acad. des Sei. de Paris, XCVIII, pp. 758-759. 
2 Djathchenko, Sophie, 1906. Zur Frage dcr Athumsorgane der Biene. 
Ann. de l’lnst. agron. de Moscou, XII, pp. 1-14. 
