The Life Processes of the Individual 153 



in respiration have been described by Carlet/ who dis- 

 tinguishes seven sets. It is stated by Djathchenko^ 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 trachese 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 jimction 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 



' Carlet, G., 1884. Sur les muscles de I'abdomen de I'abeille. Comptea 

 reudues de I'Acad. des Sci. de Paris, XCVIII, pp. 758-759. 



' Djathchenko, Sophie, 1906. Zur Frage der Athumsorgane der Biene 

 Ann. de I'lnst. agron. de Moscou, XII, pp. 1-14. 



