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for June is, that it is not in full season on the 

 Dove, in the vicinity of Ashborne, until about 

 the 4th of this month. In the smaller 

 streams in the neighbourhood, particularly 

 those that are most shaded from cold winds, 

 it appears A week earlier. In the vicinity of 

 Bakewell it appears a fortnight sooner ; and 

 on the Dove, near Rocester and Calwich, it 

 appears, generally, in the last week of May. 

 " Its season," remarks Mr. Ronalds, " depends 

 greatly upon the state of the weather ; and it 

 will be found earlier upon the slowly-running 

 parts of the stream (such as mill-dams) than 



well treated as the rest of insects. Swammerdam asserts, 

 that the ephemerae continue two or three years in their 

 larva and pupa states ; and that it is only when they have 

 attained to the utmost perfection of which their organisation 

 is susceptible, that they so speedily perish. Some of these 

 worms pass their lives in habitations, each one in his own. 

 This is nothing but a hole formed in the bed of a river ; 

 others, on the contrary, may be termed wanderers ; and 

 they are sometimes seen to swim, sometimes to walk on the 

 -various substances found in the water, and sometimes they 

 remain tranquil and concealed under a stone. Their habi- 

 tations are always made in a soft soil ; but should necessity 

 force the insect to provide a habitation in a coarser soil, it 

 takes especial care to protect its tender body by lining the 

 inside of its dwelling with fine earth. As the entrances to 

 its dwelling are situated below the surface of the water, the 

 insect is surrounded by the element, and lives for two years 

 in perfect security within its retreat. With this, as with 

 many other insects, its house not only shelters but feeds 

 it ; for it is easy to perceive through its transparent body, 

 that its intestines are filled with the same earth in which it 

 has constructed its dwelling : it is probable, that the soil is 



