70 M. G. St-Hilaire on the service which the Trochilos 



If the Trochilos is in reality the little plover, the animals 

 described by Herodotus under the name of bdella cannot be 

 leeches, (besides, leeches do not exist in the running waters of 

 the Nile,) but a very small insect of that species which swarm 

 in those damp and warm regions, known by the name of gnats 

 in Europe, and of maringouins in America. 



Myriads of these insects dance upon the borders of the 

 Nile, and when the crocodile reposes on the land he is at- 

 tacked by their innumerable swarms. His mouth is not so 

 hermetically sealed to prevent them from introducing them- 

 selves ; and they penetrate in such vast numbers, that the in- 

 ner surface of his palate, which is naturally of a bright yellow, 

 appears to be covered with a brownish-black crust. All these 

 sucking insects drive their stings into the orifice of the glands, 

 which are numerous in the mouth of the crocodile. It is then 

 that the little plover, who follows him everywhere, comes to 

 his succour, and delivers him from these troublesome enemies ; 

 — and that without any danger to himself, for the crocodile is 

 always careful when he is going to shut his mouth to make 

 some motion which warns the little bird to fly away. 



At St Domingo there is a crocodile which so nearly resem- 

 bles those of Egypt, that M. Geoffroy could not distinguish 

 them without great difficulty. This crocodile is also attacked 

 by the gnats, from which he would have no means of delive- 

 ring himself, (his tongue like that of the crocodile of the Nile 

 being fixed) if a bird of a particular species did not give him 

 the same assistance that the crocodile of the Nile receives from 

 the little plover. 



These facts explain the passage in Herodotus, and demon- 

 strate that the animal which is there called bdella is not aleech, 

 but a flying insect, similar to our gnat 



It is certain indeed that the word bdella signified in Hero- 

 dotus's time a sucker, but lately this term has been restricted, 

 and is now especially used to denote a leech. This conside- 

 ration permits us, strictly speaking, to suppose that Herodo- 

 tus was not mistaken in the facts he has related ; but we can 

 scarcely suppose that he knew positively what were the ani- 

 mals which tormented the crocodile. If he had known them, 

 he would have called them by the particular name of conops, 



