340 General Biology 



The propulsion of the muscular heart sends the blood forward 

 through various sinuses so that every part of the body is nourished 

 by it. It then returns by a closed tube, the ventral sinus, to the peri- 

 cardial sinus or chamber, and enters the heart through several pairs of 

 lateral ostia ( ). If more food has been absorbed 



than can be used, it is stored up as fat in the fat bodies on either side 

 of the heart. 



THE RESPIRATORY SYSTEM 



The blood of all insects (Fig. 220) contains a respiratory protein, 

 hemocyanin, similar to that of the crayfish. In some few species (blood- 

 worms=midge larvae, Chironomidae) hemoglobin is also found. Since 

 the hemocyanin is capable of absorbing oxygen and carbon dioxide, it 

 is probable that in the insects this respiratory protein aids the tracheae 

 in distributing oxygen and collecting C0 2 . The tracheae are kept open 

 and extended by a spiral thickening of chitinous lining and extend to all 

 parts of the body even including the legs and wings (Fig. 215, B). 



This is, no doubt, one of the reasons why the circulatory system is 



so poorly developed, for, unlike the 

 higher forms of animal life where 

 the circulatory and respiratory sys- 

 tems are dependent upon each other, 

 Fig. 220. Blood Corpuscles of the Grasshop- the systems in the insects are sepa- 



per, Stenobothrus. . , , . , . , , 



rate and distinct, so that every part 



a-f, corpuscles covered with fat-globules, r ,■• U^A * , ~ U~ ^..^^1:^^I l-t-U 



g., corpuscle after treatment with glycerine, Ot the body Can be Supplied With 



showing nucleus. (After Graber.) oxygen at any time, regardless of 



what may happen to another part. The disadvantage of such a method 

 consists in the necessity of having both a respiratory system and a 

 circulatory system in every part of the body instead of having all 

 respiratory work done in one place. The air sacs with which the 

 tracheae are connected are of value in making the animal light for flying 

 and jumping purposes. The grasshopper can beat any professional 

 human jumper by the distance it covers in a single leap when compara- 

 tive size is considered. 



If one notices a grasshopper when it breathes rapidly, it will be seen 

 that the abdomen lengthens and shortens, thus forcing air in and out of 

 the spiracles on the thorax and abdomen. 



THE EXCRETORY SYSTEM 



Like all animals, the grasshopper needs oxygen to carry on its meta- 

 bolic processes, and, like all animals, it gives off carbon-dioxide as a 

 waste product as well as water and a nitrogen-containing-substance 

 called urea (if in solution) or uric acid (if crystalline). It is interesting 

 to note that those grasshoppers, which live in dry places, excrete the 





