The Honey Bee and the Fly 



359 



THE CIRCULATORY SYSTEM 



The blood of the honey bee is quite like that of the crayfish and 

 grasshopper in being colorless and containing amoeboid corpuscles. 

 The amount of oxygen it contains is not very great. A "respiratory 

 pigment" — hemocyanin, a copper compound, gives the blood a faintly 

 bluish color, which is especially perceptible when some dozen or more 

 drops of blood are obtained. The blood acts as an aid in the fixation 

 and distribution of oxygen. 



The crayfish is also like the bee in that it has a dorsal blood vessel 

 and many sinuses, but the bee's circulatory system is even less complete 

 than that of the crayfish. 



The heart, or dorsal vessel, is a tube in the median dorsal region 

 just below the surface, closed posteriorly and open in the head-region. 

 The walls are muscular and the heart contracts at intervals. 



The blood itself enters through five pairs of ostia, one into each of 

 the five compartments into which the heart is divided. Each compart- 

 ^,-w- ment is called a ventricle. Each 



contraction sends the blood toward 

 the heart. There are valves which 

 prevent it from flowing backward. 

 It then passes through the various 

 spaces in the body to bathe the 

 tissues. As the blood passes ven- 

 trally, it is gathered into the peri- 

 cardial sinus, and, when the muscles 

 surrounding this sinus contract, the 

 blood is forced through the ostia 

 back into the heart. 



■mesa.l\ 



Fig. 234. 



A. Internal organs of the honey-bee. bt., 

 malpighian tubules; c.s., true stomach; dv., 

 dorsal vessel; e., eye; g., ganglia of nerve 

 chain; hs., honey sac; li., rectum; lp., labial 

 palpus; mesa, t., mesothorax; meta, t., meta- 

 thorax; tux., maxilla; n., nerves. No. 1, 

 No. 2, No. 3, salivary glands; oe., oesophagus; 

 p., stomach mouth; pro.t., prothorax; si., 

 small intestine (ileum) ; v., ventricles of dorsal 

 vessel. 



B. Ideal transverse section of an insect. 

 h., dorsal vessel; i., intestine; «., ventral 

 nerve-cord; t.t., stigmata leading into the 

 branched tracheal tubes; w.w., wings; a., 

 coxa of one leg; b., trochanter; c, femur; d., 

 tibia; e., tarsus. (After Packard, A, from 

 Cheshire.) 



