412 



ARTHROPODA 



An interesting adaptation of the tracheal system to acquatic life occurs in 

 the larvae of many Archiptera (dragonflies and Mayflies) and Neuroptera, and 

 even among Lepidoptera (Paraponyx) and Coleoptera (Gyrinidae). The spira- 

 cles here are usually closed, and oxygen is taken either through the skin or by 

 so-called tracheal gills bushy or leaf-like appendages of the surface or the 

 rectum, richly permeated by tracheal branches (fig. 453). In such cases the 

 tracheal system has two portions, one which receives oxygen from and gives 

 off carbon dioxide to the water; the other which supplies the tissues with oxy- 

 gen and receives carbon dioxide. 



Since the trachea?, with their fine branches, supply the tissues directly 

 with oxygen, the blood-vascular system is rudimentary. Directly under 

 the back lies the elongate tubular heart in a special pericardial sinus. 

 This is a part of the ha?moccele cut off from the gastric portion of this space 



A. 



B. 



FIG. 454. A, Male genitalia of Melolontha (from Gegenbaur, after Fab re), gl, 

 accessory glands; /, testes; vd, vas deferens; vs, seminal vesicles. B, genitalia of female 

 Hydrobius (from Gegenbaur, after Stein), be, bursa copulatrix; gl, tubular glands; 

 o, ovarial tubes; ov, oviduct with glands; rs, receptaculum seminis; v, vagina. 



by an incomplete partition in which, right and left, are the lateral muscles 

 (alee cordis) of the heart. Since folds from the margins of the ostia ex- 

 tend into the cavity of the heart, and in the systole, which proceeds from 

 behind forward, not only close the ostia, but prevent any back flow of blood 

 into the posterior part of the heart, there is an appearance of a chamber- 

 ing of the heart. The blood passes forward through an anterior aorta 

 into the ruemoccele and from this back to the pericardial sinus, the alary 

 muscles aiding by moving the viscera, and enlarging the sinus. The 

 arrangement of the viscera, fat bodies, and muscles gives a certain regular- 

 ity to the circulation, especially in the appendages. Accessory pulsating 

 ampullae in the bases of the antennae (Orthoptera) help in the flow of the 

 blood. Many beetles (Meloidas and Coccinellidse) squirt blood contain- 



