PACKARD.] PARASITES OF THE LOCUST. 665 



its life. Plate LXIII, Fig. 7,/, represents the embryo of Gordius aqua- 

 ticiis greatly magnified. It will be seen bow greatly it difrers from the 

 adult hair-worm, having in this stage some resemblance to the Acan^/io- 

 cephalus bj' its cephalic armature, to thei\>/«/i^oi<7ertorthread-worms by its 

 alimentary canal, and to the larvai [cercaria) of the Tremotodcs or fluke- 

 worms in the nature of its secretory glands. But the hair-worm differs 

 from all these worms and even biennis, a hair-worm much like and 

 easily confounded with Gordius, in having a complete metamorphosis 

 after leaving the egg.* 



When iu this stage, it incessantly protrudes and retracts its armed 

 head, the spines being directed backward when the head is out. 



In the first period of larval life the worm lives encysted in the bodies 

 of aquatic fly-larvce. The vessel in which M. Villot put his Gordius 

 eggs also contained the larva? of Tanopus, Corethra, and Clm-onomas, 

 small gnat-like flies. He found that each of these larvae contained num- 

 erous cysts with larvso of Gordius. He then removed the larvse from 

 the C3'sts, placed them on the gnat-larva, and saw the larval hair-worm 

 work its way into the head of the gnat-larva through the softer part 

 of the integument ; during the process the spines on the head, reversing 

 their usual position, enabled the worm to retain its position and pene- 

 trate farther in. Then, finding a suitable ])lace, it came to rest and re- 

 mained immovable. Then the fluids bathing the i)arts coagulated and 

 formed a hard, granulated sac. This sac at first closely env^elopes the 

 body, then it becomes looser and longer, the worm living in the anterior 

 part, the front end of the sac being probably never closed. In this first 

 larval state the worm is active. 



Ill the second larval period the young hair-worm lives motionless and 

 encysted in the mucous layer of the intestines of small fish, which prey 

 on the gnat-larvte. A minnow, for example, swallowing one of the 

 aquatic gnat-larv;e, the encysted larva becomes set free by the j^rocess 

 of digestion in the stomach of the fish; the cyst dissolving the young 

 hair-worm itself becomes free in the intestine of its new host. Imme- 

 diately it begins to bore, aided by the spines around the head, into the 

 mucous membrane lining the inner wall of the intestine of the fish, and 

 then become encysted, the worm itself lying motionless in its new home, 

 with its head retracted and the tail rolled in a spiral. The cyst is either 

 spherical or oval. (Plate LXHI, Fig. 6, g.) 



The return to a free state and an aquatic life occurs in the spring, five 

 or six months after the second encystment. It then bores through its 

 cyst, and passes into the intestinal cavity of the fish, and from thence 

 is carried out with the fjeces into the water. On contact with the water 

 great changes take place. The numerous transverse folds in the body 

 disappear, and it becomes twice as long as before, its head-armature 

 disappears, the body becomes swollen, milky, and pulpy. It remains 

 immovable in the water for a variable period, and then increases in 

 size, the integument grows harder, and when about two inches long it 

 turns brown and begins to move. Probably the host differs according 

 to chance. Most of those which have occurred in Europe reside in 



* It UKiy here be Haid that iu the Mcnnia hair-worm, which also lives iu insects, and is 

 of the same geueral appearance as Gordius, the youug when hatched is not anuulate, 

 has no cephalic armature, while the body is short and thick, the tail blunt. These re- 

 marks are based on some drawings of the eggs and embryos of a Mermis made by Mr. 

 James II. Smerton, iu Jena (May, 1876), and kindly given me by him. The female 

 genital apperturo is situated iu the middle of the body, while it is placed at the end of 

 the body iu Gordius, leading out of a cloacal chamber iu which the intestine and two 

 difterent ducts (male or female, as the case may be) termiuate, the common external 

 aperture being auo-geuital iu its nature. 



