326 



legs are thrown out at right angles to the bodj^^ so that it looks- 

 like a waterman resting on his oars. The scientific name 

 Notonecta (back swimmer), was given for a similar reason. The 

 hind legs are furnished with a fringe of hair, which enables them 

 to " feather their oars," so to speak ; as the leg is drawn forward 

 the hairs lie straight and parallel to the line of motion, but as 

 soon as a back stroke is given the hairs turn at a right angle, 

 which gives it great propulsive power. 



The rostrum of the Water-boatman is very strong and sharp, 

 and will pierce the skin if carelessly handled. -*«' 



The last that I have to mention is the large Genus Corixa, 

 which contains 28 British species, but of which the box contains 

 only one, Corixa mcesta. Of this Genus there is a Mexican 

 species, regarding which a French naturalist, M. Virlet D'Aoust, 

 has published an account. " Myriads of these little ' flies,' " he 

 says, " (Moucherous) fly about over the surface of the lake, and 

 then plunge into the water to lay their eggs at the bottom. I 

 had the advantage of being present at a great fishing for these 

 eggs, which under the Mexican name ' haoutle,' are much 

 appreciated by the Indians, who make them into a kind of cake. 

 The manner of gathering the eggs is as follows : — The Indians 

 place bundles of reeds upright in the water at some distance from 

 the bank. After ten or fifteen days these reeds will be completely 

 covered with eggs ; they are then taken out of the water and laid 

 on pieces of cloth in the sun to dry, after which the eggs are 

 easily rubbed off and the reeds are put back again." 



M. Virlet thought that these were the eggs of flies, but Guerin- 

 Meneville having received some eggs from which the " haoutle " 

 was made, determined them to be of two species, one well known, 

 as the Corixa Mercenaria, and the other he named C. Femorata. 



Pascoe in his " Zoological Classification " says, though he does 

 not give his authority, " that at the present day in the Lakes of 

 Texcona and Chalco, a white limestone rock is forming from the 

 eggs of Corixa Mercenaria. 



