572 



THE NATURE BOOK 



J^2^, 



'"^^^ 



w 



A CADDIS-CASE MADE FROM BITS OF WOOD ; AND TWO 



CASES SHOWING THE ENTRANCES. 



(Natural size.) 



Caddis dwellings is remarkable. What- 

 ever shape or appearance the structure 

 may have outside, it is invariably tubular 

 inside and comfortably Hned with silk ; 

 and, though usually just wide enough to 

 admit the creature's body, many are made 

 sufficiently roomy so that our cater- 

 pillar-like friend, when he gets tired of 

 looking out at one end of his tube, may 

 turn about and have a look out at the 

 other. 



The photograph on page 571 of a 

 group of Caddis-cases found fastened at 

 their ends to the under-side of a stone in 

 a rapid running stream shows very clearly 

 a few of the varied formations of these 

 objects. The four smallest have been 

 made from 

 bits of rushes 

 cut in exact 

 but gradually 

 diminishing 

 sizes, and 

 glued together 

 in fours so 

 as to produce 

 a rectangular 

 and tapering 

 effect. A crude 

 construction 

 is the isolated 

 example 

 above the set 

 of five, which 

 have been 

 built with mi- 

 nute stones of 

 approximate 

 size. More 

 elegant are 

 the h o r n- 

 shaped forms 

 composed of 



particles of sand and 

 grit, so equal in size and 

 so neatly cemented to- 

 gether that it is difficult 

 to believe these to be the 

 workmanship of mere 

 grubs. 



Many Caddis-worms do 

 not moor their cases to 

 stones but carry these 

 temporary habitations 

 about with them ; and 

 we frequentl}^ notice a 

 very regularly built case with a small 

 stone or a seemingly superfluous length 

 of stick attached to one end. The small 

 stone counteracts the buoyancy of a light 

 case, and the 1 )ng stick lessens the diffi- 

 culties of a fat Caddis walking under 

 water with a heavy one. 



Looking again at the horn-shaped cases, 

 we see that three of them have their 

 entrances closed. When the Caddis-worm 

 is about to change into a nymph it spins 

 a web across each end of the tube, and 

 certain species add a stone. In the 

 photograph a case is shown with the side 

 removed, thus exposing the nymph or 

 pupa enveloped in an oval covering. 

 Very likely the next stone we turn over 



" CREEPERS ■' ON THE 



UNDER SURFACE OF A WET STONE 

 MAY-FLY LARVA. 

 (Natural size.) 



AND A 



