192 NATURE'S TEACHINGS. 



On the other side is an object, which at a hasty glance 

 might be taken for another Window of the same character. It 

 is, however, the work of an insect, and not of man, and is 

 magnified in order to show its structure better. 



Any of my readers who may happen to be entomologists or 

 anglers, or both, are familiar with the Caddis- worm of our fresh 

 waters. Most of us know that the Caddis is the grub or larva 

 of the Stone-fly (Phryganed), an insect haunting the water- 

 side, and so moth-like in its general aspect that many persons 

 think that it is really a brown moth. The changes or meta- 

 morphoses of these insects are well worthy of notice. 



In one respect the Caddis resembles the larva of the "Wax- 

 moth, mentioned on page 151, inasmuch as it has a soft, defence- 

 less body, while the first three segments are comparatively 

 hard. Like the Wax-moth also, the Caddis lives in a tube 

 constructed by itself. Instead, however, of having a long and 

 fixed tube, up and down which it can pass at pleasure, the 

 Caddis makes a tube only a little longer than its body, and 

 light enough to be carried about, just as the hermit-crab carries 

 its supplementary shell. There are many species of Caddis-fly. 



The Caddis inhabits fresh waters, and cares nothing whether 

 they be ponds or running streams. In order to defend its 

 white, plump, and helpless body from the fishes and other 

 enemies, it constructs a tube around its body, strengthening it 

 by a wonderful variety of material according to the locality. 



Mostly the tubes are covered with little pieces of stick or 

 grass, or leaves, while some species use nothing but sand-grains, 

 constructing with them a tube very much resembling in shape 

 an elephant's tusk, and reminding the conchologist of the 

 dentalium shell. But they seem to use almost anything that 

 comes to hand. Taking only examples found by myself in a 

 single pond, these cases are formed of sand, stones, sticks, grass- 

 stems, leaves, shells of small water-snails, mostly the flat 

 planorbis, the opercula of the water-snail, empty mussel- shells, 

 a chrysalis of some moth which had evidently been blown into the 

 water from an overhanging tree, and acorn-cups. The larva, 

 however, does not seem to be able to fasten together any objects 

 with smooth surfaces, and though it has been known, when in 

 captivity, to make its cases out of gold-dust or broken glass, it 

 could not use either material when in the form of beads. 



