ON ENTOMOLOGY. 



alone could be distinguished. Each of these Flies, after having de- 

 scribed one or two orbits, fell to the earth or into the water, though not 

 in consequence of being burned. He says, it is astonishing that the 

 Ephemera, which appearing after sunset and dying before sunrise, are 

 destined never to behold the dawn of day, should have so strong an 

 inclination for any luminous object. Some of our British Ephemerae 

 begin their dances with the dawn instead of waiting till sunset, rising 

 and falling continually over the meadows in May ; sometimes beating 

 the air rapidly with their wings, and sometimes skimming about like 

 hawks. 



There is a very interesting class of Grubs which live under the 

 water, where they construct for themselves moveable tents of various 

 materials as their habits direct them, or as the substances they require 

 can be conveniently procured. Among the materials used by these 

 singular Grubs, well known to fishermen by the name of Caddis Worms, 

 and to naturalists as the larva of four-winged Flies, we may mention 

 sandstones, shells, wood, and leaves, which are skilfully joined, and 

 strongly cemented. One of these Grubs forms a pretty case of leaves 

 glued together longitudinally, but leaving an aperture sufficiently large 

 for the inhabitant to put out its head and shoulders when it wishes to 

 look about for food. Another employs pieces of reed cut into conve- 

 nient lengths, carefully joining and cementing each piece to its fellow 

 as the work proceeds, and he frequently finishes the whole by adding a 

 broad piece longer than the rest to shade his doorway overhead, so that 

 he may not be seen from above. A more laborious structure is reared 

 by the Grub of a beautiful Caddis Fly (Phryganea), which weaves to- 

 gether a group of the leaves of aquatic plants into a roundish ball, and 

 in the interior of this forms a cell for its abode. Another of these 

 aquatic architects makes choice of the tiny shells of young fresh water 

 muscles and snails (Planorbis), to form a moveable grotto ; and as 

 these little shells are for the most part inhabited, he keeps the poor 

 animals close prisoners, and drags them without mercy along with him. 

 These grotto buildings are by no means uncommon in ponds and in 

 chalk districts, such as the country about Woolwich and Gravesend. 

 One of the most surprising instances of their skill occurs in the struc- 

 tures, of which small stones are the principal material. The problem 

 is to make a tube about the width of the hollow of a wheat straw or a 

 crow quill, and equally smooth and uniform. Now, the material being 

 small stones full of angles and irregularities, the difficulty of perform- 

 ing this problem will appear to be considerable, if not insurmountable ; 

 yet the little insects, by patiently examining their stones, and turning 

 them round on every side, never fail to accomplish their plan. This, 

 however, is only part of the problem which is complicated with another 

 condition, namely, that the under surface shall be flat and smooth, with- 

 out any projecting angles, which might impede its progress when 

 dragged along the bottom of the rivulet where it resides. The selection 



