1 98 The Field Naturalisfs Quarterly Aug. 



hatching of the eggs of different species, some breaking 

 the shells in seven days, and others (it is said) appearing 

 after as many months. There is also a great difference in 

 the structure and habits of the larvae when hatched; although 

 all have this in common, that they cannot live out of water. 

 There are, first, the burrowers, with long bodies, small 

 heads, and forelegs adapted for digging. These live in 

 slow streams, tunnel the clay or earth of the banks, and 

 eat minute animal substances contained in the soil in which 

 they dwell. Then come a set with flattened bodies, found 

 in clear, strong streams. They cling to the stones with 

 their very broad legs, and feed on the small water-insects 

 which come within their reach. A third section live in 

 ditches and pools, and having no fear of being swept away 

 by the current, use their excellent tail fins to propel them 

 through the water in pursuit of the small creatures on which 

 they feed. Lastly, we have a group which are content with 

 creeping on the bottom of streams ; compensating for their 

 lack of swiftness by using a covering of mud as a disguise 

 while hunting their prey. 



The breathing apparatus of the larvae (which has to be 

 entirely remodelled when they sail off into the air) is of a 

 very efficient nature, one species having such excellent gills 

 that they are said to be superior to those of any other aquatic 

 insect. While in the water the young may-flies increase in 

 size by a series of moults, to the number of twenty or more, 

 so that the same skin does not serve them long. As they 

 grow faster in summer than in winter, they then change 

 their costume oftener. The burrowing group have a curious 

 habit of making two doors to their houses at a little distance 

 from each other, so that if a disagreeable visitor appears at 

 one door the owner is able to depart by the other. 



If the lives of may-flies ended at the expiration of a couple 

 of years spent in the water, little would be heard of their 

 history ; but the extraordinary swarms which emerge in 

 summer, engage in elegant dances in the air, and die be- 

 fore the rising of another sun, have attracted attention 

 to them. I remember alighting at a railway station in 

 Switzerland, near a small river, and finding the platform 

 covered with may-flies, while others were fluttering and 



