ANATOMY AND PHYSIOLOGY 113 



and even in the detached abdomen of a grasshopper or dragon fly. Each 

 ventral ganglion of the body is an independent respiratory center for its 

 particular segment. 



10. REPRODUCTIVE SYSTEM 



The sexes are always separate in insects, hermaphroditism occurring 

 only as an abnormal condition. The sexual organs, situated in the ab- 

 domen, consist essentially of a pair of ovaries or testes and a pair of ducts 

 (oviducts or seminal ducts, respectively). Primitively, the ducts open 

 separately, as they still do in Ephemeridae, but in almost all other insects 

 the two ducts enter a common evacuating duct (vagina or ejaculatory 



FIG. 179. Reproductive system of male FIG. 1 80. Reproductive system of 



beetle, Melolontha. a, accessory gland; c, copu- male Lepidoptera. a, accessory gland; 



latory organ; d, ejaculatory duct; s, seminal d, ejaculatory duct; t, united testes; v, 



vesicle; /, testis; v, vas deferens. After KOLBE. vas deferens. After KOLBE. 



duct)', this opens ordinarily between the penultimate and antepenulti- 

 mate segments of the abdomen, i. e., usually the ninth and eighth, at any 

 rate never through the last abdominal segment. 



Homologies. As in other animals, the reproductive organs are 

 homologous in the two sexes. Thus: 



MALE. FEMALE 



Testes = Ovaries 

 Seminal ducts = Oviducts 

 Ejaculatory duct = Vagina 



Seminal vesicle = Seminal receptacle 

 Accessory glands = Accessory glands 

 Penis and accessories = Ovipositor 



Male Organs. Each testis, though sometimes a single blind tube, is 

 usually a group of tubes or sacs (Fig. 179), testicular follicles, which open 

 9 



