IV. INSECTA: HEXAPODA. 



471 



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

 noteworthy that many beetles (Meloidae and Coccinellidae) squirt 

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

 protection. 



The Hexapoda are dkscious. The gonads consist of a few or 

 many ovarial or testicular tubules (figs. 496, 497), 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- 



FIG. 496. 



FIG. 497. 



FIG. 496. Male genitalia of Melolontha. (From Gegenbaur, after Fabre.) gl, accessory 



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

 FIG. 497. Genitalia of female Hydrobius. (From Gegenbaur, after Stein.) be, bursa 



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



ceptaculum seminis; v, vagina. 



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

 all other Hexapoda 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 ejaculatorius of the male, the vagina of the female. Aside 

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

 ing differentiations: in the male vesiculaa 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- 



