332 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION, 



TJie 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 intes- 

 tinal cavity of the fish, and from thence is carried out with the faeces 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 dis- 

 appears, the body becomes swollen, milky, and pulpy. It remains iDimovable 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. 



Thus the development of the hair-worms of the genus Gordius would 

 seem to be pretty well made out. Hatching in the water 5 penetrating 

 the soft larvae of aqu9,tic flies and there encysting, the young Gordius 

 is taken into the stomachs of fishes, becomes freed and again encysts 

 in the mucous layer of the stomach ; it finally bores through its cyst 

 and is passed out with the fish's faeces into the water, in which it takes 

 on its final growth. 



JLt is difficult to conceive how these parasites could ever infest insects 

 like locusts, which preferably dwell in dry places, and still more difficult 

 to understand how they could affect katydids, that dwell high up on 

 trees or shrubs,^^ if they are all as essentially aquatic as those studied 

 by M. Yillot. It is true that those beetles which frequent moist ground 

 (like the CaraUdce) and those spiders which live in the ground are most 

 infested: while it has been observed that the hair-worms are most com- 

 mon during wet weather and more often found in locusts that dwell in 

 low meadows than in those inhabiting higher and drier regions. Still 

 these several insects could not well be affected by a purely aquatic para- 

 site, and the probability is that the hair-worms belonging to this genus 

 are not particular as to their host; and will develop in soft-bodied terres- 

 trial as well as aquatic animals. For it is self-evident that most of those 

 which infest such insects as we have mentioned cannot possibly reach 

 water upon leaving their victims. 



^ow, either these specimens perish without issue if they fail to reach 

 water, or their young can develop in other soft larvae dwelling in or upon 

 the earth, and the latter supposition seems the most probable from the 

 circumstances. Yet even on this supposition the mode by which they 

 get into tree-inhabiting insects and such as never descend to the earth, 

 remains as much as ever a mystery, and a further effort of the imagina- 

 tion is necessary to meet the case. We venture the explanation, bold 

 as it may seem, that the excessively minute ova separate and scatter in 

 the water and are sometimes drawn into the air by rising currents or 

 blown into it by winds, either from the surface of pools and ponds, or 

 of the earth 5 and that permeating the atmosphere, like the spores of 

 fungi and many other minute organisms, they are occasionally brought 

 by rains or heavy dews into contact with those insects and other ani- 

 mals in which they are known to develop. In pools, ponds, or sloughs 

 that dry up in summer, there will be Gordius eggs on the surface of the 



8° As in the case of Mermis acuminata infesting the Apple-worm. 



