WATER INSECTS AND THE RISE 65 



or more weeks, flying with the breeze, generally down- 

 stream. In this stage of its life it can be easily recognised 

 by its comparatively heavy, drifting flight, and its dull, 

 semi-opaque appearance. By the aid of a watchmaker's 

 glass, cilia will be seen covering the surface, and forming a 

 fringe to the posterior margin of its wings. 



The sub-imago stage of its life, which is very brief in some 

 cases, is finally forsaken when the entire membrane of its 

 body and wings again splits open and is discarded, and the 

 insect then assumes its perfected stage as the imago or 

 spinner. 



It is now fully matured and enters into its bridal existence, 

 which lasts but a few days. In this stage it is to be seen in 

 great numbers when the heat is not excessive and during 

 the evening hours. Its wings are now gauzy and its body 

 lighter and more brilliant in colour. It is easily recognised 

 as it soars, floats, and sinks in the ambient summer atmo- 

 sphere. 



The following are the popular names by which some of the 

 forms of the Ephemeridae are known : Olive Duns, Duns, 

 Blue Duns, Autumn Duns, Blue- Winged Olives, Iron Blue 

 Duns, Red-Quill Duns, Red Spinner, Jenny Spinner, May- 

 fly, March Brown, Iron Blue, etc. 



THE TRICHOPTERA, OR CADDIS-FLY 

 These insects, unlike those of the Ephemeridae and 

 Perlidae family, undergo a distinct metamorphosis during 

 their sub-aqueous existence. 



The Trichoptera may be divided into two families. 

 The larva of one, after leaving its egg, spins a cylindrical 

 sheath round itself (see Plate VII., Fig. 2), which forms its 

 future home, and to which it attaches small stones, sand, 

 wood, etc. ; these cover and mask this case, and at the same 

 time act as ballast. The case thus forms an armour-like 



