ANCIENT ANGLING AUTHORS 215 



lished in " Low-Dutch," by Jo. Swammerdam, M.D., 

 of Amsterdam, in 1675, and was translated into Eng- 

 lish by a friend of Dr Tyson in 1681. 



This monograph on the May-fly consists of 44 

 quarto pages, and 8 plates, illustrating the fly and the 

 larva, are inserted at the end of the work. With the 

 exception of the description of the method of genera- 

 tion of the flies and the duration of their existence, 

 the account given is interesting, exhaustive, and for 

 the most part accurate. 



Swammerdam confesses that he does not know how 

 long it is before the larva hatches out of the egg, but 

 suggests that by keeping some of the eggs " in a 

 vessel with water and clay, some knowledge thereof 

 might be obtained " ; Mr Halford, who has conducted 

 this experiment, found that the eggs hatched out in a 

 little less than ten weeks. The larvae belong to the 

 class known as digging larvae, and as soon as they 

 are hatched they bury themselves in the bed of the 

 river; it is not known for certain how long they 

 remain in the larval condition, but it is certainly two, 

 and possibly three years. Swammerdam states that 

 they remain three years in this stage of their 

 existence, that a larva one-year-old is f of a Holland 

 inch in length, a two-year-old is if inch long, the 

 wing cases having then appeared, a three-year-old 

 larva is 2\ Holland inches in length, and the wing 

 cases are more plainly seen. 



It is interesting to compare Mr Halford's account 

 of the metamorphosis of the nymph (a larva is called 



