NO. 2131. 



NEMATODE PARASITE!^ OF RODENTS— HALL. 



195 



Female 60 to 80 mm, long and 170 to 326 p. thick. Cuticle to 12 [;. 

 thick. Lateral lines 120 ]x wide. Pharynx 53 [;- long and 20 \x thick 

 in a 60 mm. long specimen. The esophagus is one-ninth of the entire 

 length of the worm. The vulva is near the posterior extremity, at 

 a distance of one-eighth to one-tenth of the body length, and is not 

 prominent. The vagina extends anteriorly from the vulva for a 

 short distance and the uteri are divergent. The anterior uterus be- 

 comes the receptaculum seminis near the posterior 

 extremity of the esophagus and the posterior uterus 

 becomes the receptaculum seminis posterior of the 

 vulva. Each uterus communicates with a short 

 curved oviduct and these in turn with the ovaries. 

 The initial portion of the anterior ovary is directed 

 posteriorly and the initial portion of the posterior 

 ovary is directed anteriorly. The ovaries are very 

 much looped, the long axis of the loops paralleling 

 that of the body. Eggs are regularly ovoid, with a 

 maximum size of about 60 by 40 (i in diameter. In 

 optical section they are somewhat thickened at the 

 poles, with a line of distinct demarcation between 

 the thinner shell in the middle of the egg and the 

 thicker shell at the poles. Eggs always contain em- 

 bryos when oviposited. The embryo is thickest at 

 the anterior end and diminishes in size cA^enly to the 

 posterior end. 



Life history. — Eggs passing from the female into 

 the host epithelium around the worm are passed out 

 in desquamation of the epithelium. Thej^ may be 

 left in moist feces half a year without alteration. If 

 fed to certain insects {Periplaneta americana, Pcri- 

 planeta orientaUs, Blatta (Ecfohia) gerinanica., or 

 Tenehrio molitor) or ingested naturally by these in- 

 sects, the embryos escape from the eggs, the thick- 

 ened polar portions of the shells being removed under 

 .the action of the digestive fluids. This embryo is 250 

 IX long and 13 /x thick, with the cuticle somewhat thickened anteriorly 

 and with no internal differentiation. The day after feeding, these 

 embryos and the empty shells are found in the intestine. The next day 

 neither are found, and the subsequent wanderings or location of the 

 worms is not known until they are found encapsulecl in the musculature 

 of the prothorax and of the limbs of the insect about 20 days later. 

 The capsule is not very prominent. The larvae are coiled in a 

 spiral, usually with the tail in the center and the head at the periph- 

 ery. This larva is 792 [/. to 1.215 mm. long and rather slender. It 



Fig. 253.— Gongti.0- 

 nema neoplasti- 

 ctTM. Labva 



FROM PROTHORAX 



o F Periplaneta 



AMERICANA. EN- 

 LARGED. After 

 FrnlGER AND Dit- 

 LEVSEN, 1014. 



