412 



ARTHROrODA 



An intcrcstin,!:; adaptation of tlic tracheal system to acquatic life occurs in 

 the lar\:e of many Archiptera ^drasjontlies and Mayflies) and Xeuroptora, and 

 even anions; Lepidoptera (Pardp,>iiYx) and Coleoplera (Gyrinidii;). The spiira- 

 eles here are usually closed, and oxvL,'en is taken either through the skin or Ly 

 so-called tracheal trills — Inishv or leaf-like appendages of the surface or the 

 rectum, riclilv permeated by tracheal branches (t'lg. 453V In such cases the 

 tracheal svstem has two portions, one which receiws 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 trachex. with their line branches, supply the tissues directly 

 with oxvgen, the blood-\-ascular system is rudimeiilary. Directly under 

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

 Tliis is a part of tlie kemoccEle cut oft from the gastric portion of tliis space 



.-1. 



D. 



Fig. 434. — . 1. Male genitalia of Mdohnitha (from Gcgcnbaur. after Fabre). g!, 

 accessor>" glamls; /, testes; vd, vas tlefcrcns; ^L'^^ seminal ■\"csicles. B. genitalia of female 

 HYdrohius (from Gegenbaur, after Stein), be, bursa copulatrix; s;/, tubular gkinds; 

 o, ovarial tubes; in', oviduct with glands; rs, rcceptaculum seminis; v, vagina. 



by an incomplete partitioii in wliich, right and left, are the Literal muscles 

 (aUc cordis) of the heart. Siitce folds from the margins of the ostia ex- 

 tend into the ca\ity of the heart, and in the systole, wliich proceeds front 

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

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

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

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

 muscles aiding by moving the viscera, and enlarging the sinv.s. The 

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

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

 ampulkv in the bases of the antenna^ (Orthoptera) help in the llow of the 

 blood. Many beetles (Meloida^ and Coccinellidx) scjuirt blood contain- 



