■26 NEW ZEALAND NEUBOPTERA. 



The perfect May-fly takes no food ; its alimentary canal 

 gradually becomes distended with air, afterwards acting as 

 a kind of balloon, whilst the insects are performing their 

 well-known aerial dances. During these flights the May- 

 flies rise and fall in the air, almost in perpendicular lines, 

 and it is at this time that the pairing of the sexes takes 

 place. Of these remarkable dances it has been well said * 

 that to the May-flies themselves, the movements may, by 

 the number of the separate eyes, by their curved surfaces, 

 and by the innumerable facets composing them, be 

 multiplied and correlated in a manner of which our own 

 sense of sight allows us to form no conception. We can 

 see on a summer's evening how beautifully and gracefully 

 a crowd of May-flies dance, and we may well believe that 

 to the marvellous ocular organs of the flies themselves, 

 these movements form a veritable ballet. It has already 

 been explained that during these dances the stomach of 

 the May-fly becomes distended with air, and it is further 

 believed that the contents of the sexual glands are driven 

 along their simple and direct canals f by the expansion of 

 the balloon-like stomach. During these dances the 

 momentary conjugation of the sexes occurs, and imme- 

 diately thereafter the female, according to Eaton, resorts to 

 the waters for the appropriate deposition of her eggs. As 

 regards this, Eaton says : " Some short-lived species 

 discharge the contents of their ovaries completely 

 en masse, and the pair of egg clusters laid upon the water 

 rapidly disintegrate, so as to let the eggs sink broadcast 

 upon the river-bed. The less perishable species extrude 

 their eggs gradually, part at a time, and deposit them in 

 one or other of the following manners : Either the 

 mother alights upon the water at intervals to wash off the 

 eggs that have issued from the mouths of the oviducts 

 during her flight, or else she creeps down into the water 

 to lay her eggs upon the under side of stones, disposing 

 them in rounded patches, in a single layer evenly spread, 

 and in mutual contiguity." The eggs are very numerous, 

 and it is thought may sometimes remain in the water as 

 long as six or seven months before they hatch. The 

 number of individuals produced by some kinds of May- 



* Sharp, " Insects," 440 et seq. 



t The sexual organs of the Ephemeridee are remarkable for their simplicity, 

 and for the fact that the ducts by which they communicate with the exterior 

 continue as a pair to the extremity of the body and do not, as in other 

 insects, unite into a common duct. This extraordinary structure exists in 

 both sexes. 



