156 Annals Entomological Society of America  [Vol. XIV, 
On this basis, the role of insect blood may be summarized as follows: 
The blood is instrumental (1) in circulating food, (2) transporting 
metabolic products (enzymes, pigments, etc.), (3) 1n respiration in the 
distribution of oxygen and removal of carbon dioxide. 
Be it noted that the last of these, the role in respiration, is not con- 
fined to aquatic larvee alone—that is, larvee provided with blood gills. 
On the contrary, the role of the blood is identical in all insects, regardless 
of the stage. For the tests for respiratory proteins (oxidation and 
incineration) were performed on all types of insects, regardless of 
habitat, stage, and food habit of the species. . 
V. SUMMARY. 
1. Both oxygen and carbon dioxide are present in insect 
blood. A small portion of these gases is probably dissolved in 
the blood serum, the major portion is held by a respiratory 
protein. 
2. A respiratory protein was demonstrated for all insects 
through reactions with oxidation tests for hemoglobin. Hemo- 
globin is possessed exclusively by Chironomid ‘‘blood-worms”’ 
among insects. All other insects show the presence of copper, 
which is interpreted as forming the nucleus of another 
respiratory pigment, hemocyanin. 
53. This hemocyanin is possessed by all insects, regardless of 
stage, habitat, or food. The source of this copper was shown 
to be the water, soil, and food plants. 
4. The role of insect blood is therefore, in addition to its. 
recognized function of circulating food and metabolic products, 
to aid the tracheal system in the distribution of oxygen to the 
tissues and to remove the carbon dioxide. 
VI. BIBLIOGRAPHY. 
Muttkowski, R. A. The Respiration of Aquatic Insects: A Collective Review. 
Bull. Brooklyn Ent. Soc., 15, pp. 89-96, 131-140, 1920. 
Rose, W. C., and Bodansky, M. Biochemical Studies on Marine Organisms: I. 
Copper in Marine Organisms. Jn. Biol. Chem., 44, pp. 99-112, 1920. 
