6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



2. Only male known, 23 mm. long by 5Q4fi wide ; spicules 622/a and 1.1 mm. 



long P. gracilis. 



Both male and female known, the male not ns slender as 564/i4 ; spicule 



lengths different from those of P. gracilis 3. 



H. Median lobe of lips tootliless ; vulva at level of posterior third of body, 



dividing body length in ratio of 2 : 1 ; spicules equal, 395^1 long P. bonnet 



Median lobe of lips with teeth ; vulva anterior to middle of body ; spicules 

 unequal, the long spicule always more than 395^1 4. 



4. Long spicule not over 830/^; short spicule not over 420;ii 5. 



Long spicule over 1 mm. ; short spicule 622/li or longer 6. 



5. Long spicule 830|it ; short spicule 420^ P. numidica. 



Long spicule 480;U ; short spicule 350ju P. muricola. 



6. Vulva a little anterior of union of anterior and middle third of body ; dif- 



ference in length of the 2 spicules more than 500fi P. ascaroidea. 



Vulva slightly anterior of middle of body ; difference in length of the 2 

 spicules not over 300^ 7. 



7. Male not over 28 mm. long; female not over 40 mm. long; median lobe of 



lips with a large central tooth and 2 smaller teeth on each side : tail of 



male 1/41 of total body length P. muris. 



Male up to 43 mm. long ; female up to 100 mm. long ; median lobe of lips 

 with a long central tooth and 4 or 5 smaller teeth on each side ; tail of 

 male 1/50 of total body length P. columMana, 



SUMMARY. 



A new species of nematode, Protospirura columhiana, was found 

 in the stomach and esophagus of wild rats {Rattus norvegicus) 

 killed at the National Zoological Park, Washington, D. C. Life 

 history experiments resulted in the successful development of the 

 encysted larval stage of the nematode in cockroaches (croton bugs, 

 Ectobia gerinanica). The larvae begin to encyst about one month 

 after the eggs are fed to the roaches, but they are apparently not 

 infective at that time. After 41 days they appear to have reached 

 the infective stage, one of the larvae being present in the stomach 

 of a mouse at its death 2 days after the feeding of the encysted 

 form. Adult nematodes were developed in rats by feeding the 

 encysted larvae obtained from a roach 58 days after the latter was 

 fed the embryonated eggs. The nematodes arc still immature 35 

 days after the feeding of the final host; after 53 days they are 

 mature but not fully grown, whereas after 115 daj^s they have at- 

 tained the size of the majority of the nematodes found in natural 

 infections. 



The onl}' other life history of a species of Protospirura that ap- 

 pears to be known is that of P. muris. Leuckart (1867) and Marchi 

 (1871) found that encapsuled larvae develop in meal worms, 

 Tenebrio species, about 5 weeks after the nematode eggs had been 

 eaten by the worm. 



The finding of P. Columbiana in wild rats in the Zoological Park 

 but not in those from other parts of the city suggests the possibility 



