IV. INSECTA : IIEXAPODA. 



471 



the antennas (Orthoptera) help in the flow of the blood. It is 

 noteworthy that many beetles (Meloidfe and Coccinellidffi) squirt 

 blood through the jointing membranes of the legs as a means of 

 protection. 



The Hexa23oda are dicEcious. The gonads consist of a few or 

 many ovarial or testicular tubules (figs. 496, 407), the latter some- 

 times coiled into small oval bodies. Ovaries and testes are paired 

 and lie, right and left, in the abdomen. Their paired ducts (ovi- 



FlG. 496. 



Fig. 497. 



Fig. 496. — Male genitalia of ifelnlontha. (From Gegenbaur, after Fabre.) gl, accessory 



glands; t, testes; vd, vas deferens; vs, seminal vesicles. 

 Fig. 497.— Genitalia of female i/j/dro6m.'!. (From Gegentaauer, after Stein.) 6c, bursa 



copulatrix; gl, tubular glands; o, ovarial tubes; ou, oviduct with glands; rs, re- 



ceptaculum seminis; v, vagina. 



ducts, vasa deferentia) open separately in the Ephemerida, but in 

 all other Hexaj^oda there is a single ventral unpaired sexual open- 

 ing just in front of the anus. This arises as a median invagination 

 of the ectoderm (hence lined with chitin), which extends inwards 

 and meets the genital ducts (modified nephridia), and forms the 

 ductus ejac^"llatorius of the male, the vagina of the female. Aside 

 from many accessory glands, the sexual apparatus shows the follow- 

 ing differentiations: in the male vesiculas seminales, as widenings 

 or diverticula of the vasa deferentia; in the female the receptaculum 

 seminis and the bursa copulatrix. The latter may be either the 

 vagina or a blind sac arising from it, or a special invagination of 

 the ectoderm, emptying into the vagina by an internal canal. It 

 receives the penis. The receptaculum seminis, a stalked vesicle 

 connected with the vaginia or the bursa, has a special biological 

 interest. In insects which copulate but once during life it retains 

 the spermatozoa for a long time — four years in bees — in a living 

 condition. As the eggs are laid they are impregnated by sperma- 



