1902 Lives Measured by Mimttes 197 



lives are longer than those of any other known insect. 

 May-flies have been taken by the poets as the type of the 

 brevity of life, and the name Ephemera has been conferred 

 upon them. This is justified by the fact that their mature 

 existence lasts in some species for only an hour, or even 

 less ; the insects emerging from the water on a summer's 

 evening, soaring aloft, depositing their eggs, and dying, 

 almost like a flash of light. But as the fruit of autumn 

 is the crown of all the preceding months, so the activity 

 of may-flies is only the culmination of their career, for it 

 has been preceded by a two years' existence as a grub in 

 the water. 



There are at least 300 species known to science, about 40 

 of which are found in Britain. They are related to the 

 dragon-flies, and possess four wings covered by innumerable 

 veins, the hinder pair being much smaller than those in 

 front, in contrast to those of their fierce cousins, whose 

 wings are almost equal in size. As may-flies do not take 

 food when mature, their mouths are practically useless ; but 

 what they lack in taste they make up in sight, the males 

 of some species having no fewer than seven eyes — two in the 

 ordinary position, three on the forehead, and two standing 

 up as pillars behind them. Although they are exceedingly 

 fragile, may-flies have left their signature on the solid rocks, 

 their fossil remains found in very ancient strata showing 

 that they existed in abundance in the far-off days when the 

 coal which we are now burning flourished as living plants. 



But begin at the beginning — namely, with the eggs. 

 Naturally enough there is some diversity in the method of 

 depositing these. Some species exercise care, and appar- 

 ently attach them to stones and weeds under water ; but 

 the majority simply drop them overboard in two compact 

 masses embedded in jelly, each mass containing about 350 

 eggs. The covering quickly dissolves on contact with the 

 water, and the eggs, instead of remaining in a heap, are 

 sown broadcast over the bottom of the quiet river or pond 

 selected to be their future home. Many eggs have curious 

 appendages, which serve as hooks to keep them from floating 

 down the stream. 



There is a great diversity in the time required in the 



