114 



ENTOMOLOGY 



into a seminal duct (vas defer ens). In most Lepidoptera the testes are 

 secondarily united into a single mass (Fig. 180) as also in Acridiidae. 

 The two seminal ducts enter the common ejaculatory duct, which termin- 

 ates in the intromittent organ, or penis. Often each vas deferens is di- 

 lated near its mouth into a seminal vesicle, or reservoir; or there may be 

 only a single seminal vesicle, arising from the common duct. One or 

 more pairs of glands opening into the vasa deferentia or the ductus ejac- 

 ulatorius secrete a fluid which mixes with the spermatozoa and oftentimes 



unites them into packets, known as spermato- 

 phores. 



All these parts are subservient to the forma- 

 tion, preservation and emission of the spermatozoa. 

 These minute, thread-like bodies (Fig. 181) arise 

 in the testicular follicles from a germinal epithe- 

 lium, and consist, as in vertebrates, of a head, 

 middle- piece and a vibratile tail without enter- 

 ing into the finer structure. 



Female Organs. Each^ary (Fig. 182) con- 

 sists of one or more tubes opening into an oviduct. 

 The two oviducts enter a common duct, the 

 vagina, which opens to the exterior, often through 

 an ovipositor. Frequently the vagina is expanded 

 as a pouch, or bursa copulatrix, though in Lepidop- 

 tera the bursa and the vagina are distinct from 

 each other and open separately (Fig. 183). In 

 most insects a dorsal evagination of the vagina 

 forms a seminal receptacle, or spermatheca, from 

 which spermatozoa emerge to fertilize the eggs. 

 The accessory glands, either paired or single, 

 provide a secretion for attaching the eggs to 



foreign objects, cementing the eggs together, forming an egg-capsule, etc. 

 In each ovarian tube, or ovariole, are found ova in successive stages of 

 growth, the largest and oldest ovum being nearest the oviduct. In the 

 primitive type of egg-tube, as in Thysanura and Orthoptera (Fig. 184, 

 A) every chamber contains an ovum; in more specialized types, every 

 other chamber contains a nutritive cell instead of a germ cell, the nutri- 

 tive cells serving as food for the adjacent ova (B] ; or the nutritive cells, 

 instead of alternating with the ova, may be collected in a special chamber, 

 beyond the ovarian chambers (C). An egg-tube is usually prolonged dis- 

 tally as a terminal filament or suspensor, the free end of which is attached 

 near the dorsal vessel. 



FIG. 181. Sperma- 

 tozoa. A, locustid grass- 

 hopper; B, cockroach, 

 Blatta; C, beetle, Copris. 

 After BUTSCHLI and BAL- 

 LOWITZ. 



