Other Nematodes Developing in Arthropods 
183 
122. Cyclops, the 
intermediate host of 
Dracunculus. 
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 muscce 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, i860, 
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. 
