Other Nematodes Developing in Arthropods 183 



The female worm is excessively long and slender, measuring nearly 

 three feet in length and not more than one-fifteenth of an inch in 

 diameter. It is found in the subcutaneous connective tissue and when 

 mature usually migrates to some part of the leg. 

 Here it pierces the skin and there is formed a small 

 superficial ulcer through which the larvae reach the 

 exterior after bursting the body of the mother. 



Fedtschenko (1879) found that when these larvae 

 reach the water they penetrate the carapace of the 

 little crustacean, Cyclops (fig. 122). Here they molt 

 several times and undergo a metamorphosis. Fedts- 

 chenko, in Turkestan, found that these stages required 

 about five weeks, while Manson who confirmed these 

 general results, found that eight or nine weeks were 

 required in the cooler climate of Engand. 



Infection of the vertebrate host probably occurs through swallow- 

 ing infested cyclops in drinking water. Fedtschenko was unable to 

 demonstrate this experimentally and objection has been raised against 

 the theory, but Leiper (1907), and Strassen (1907) succeeded in infest- 

 ing monkeys by feeding them on cyclops containing the larvae. 



Habronema muse is a worm which has long been known in its 

 larval stage, as a parasite of the house-fly. Carter found them in 

 33 per cent of the house-flies examined in Bombay during July, 1860, 

 and since that time they have been shown to be very widely distrib- 

 uted. Italian workers reported them in 12 per cent to 30 per cent 

 of the flies examined. Hewitt reported finding it rarely in England. 

 In this country it was first reported by Leidy who found it in about 

 20 per cent of the flies examined at Philadelphia, Pa. Since then it 

 has been reported by several American workers. We have found it 

 at Ithaca, N. Y., but have not made sufficient examinations to justify 

 stating percentage. Ransom (1913) reports it in thirty-nine out of 

 one hundred and thirty-seven flies, or 28 per cent. 



Until very recently the life-history of this parasite was unknown 

 but the thorough work of Ransom (1911, 1913) has shown clearly 

 that the adult stage occurs in the stomach of horses. The embryos, 

 produced by the parent worms in the stomach of the horse, pass 

 out with the feces and enter the bodies of fly larvae which are develop- 

 ing in the manure. In these they reach their final stage of larval 

 development at about the time the adult flies emerge from the pupal 

 stage. In the adult fly they are commonly found in the head. 



