SYNOPSIS OF THE EPHEMERID.E 15 



mayfly. He examines it, and turning to the 

 table finds : i. Tail bristles three in number, 

 all nearly of the same length. This describes 

 the insect in his hand, and at the end of the line 

 he finds the number 2. He refers to the para- 

 graph indicated i.e. with the No. 2 on the left- 

 hand side and reads, Wings four in number . . 3. 

 This is also descriptive of his mayfly, so he dis- 

 regards the alternative and goes on to paragraph 

 3, as directed on the right-hand side. Para- 

 graph 3 is a little more complicated, but as his 

 fly is of a fairly large size he passes on to 4, 

 and there runs his quarry down, either by the 

 spotted wings or, with more certainty, the form 

 of the forceps-limbs of the male. If, however, 

 when at 3, he had accepted the alternative, he 

 would then have had to pass on to 5 or 6, and 

 would have found that all the insects therein 

 described possessed forceps-limbs composed of 

 three joints, whereas in the fly under examina- 

 tion four joints are present, and this should 

 send him back again, and put him on the right 

 track. 



