i6o POPULAR SCIENCE MONTH/ v. 



sand is loose and desert-like for about two inches in depth, after 

 which it meets sand finer in grain and baked hard. The larger grit 

 lies on the surface. If you look carefully at these patches, you may 

 see a delicate outline, shaped like a butterfly's wings, traced on the 

 red sand, one pair of 'wings' being generally larger than the ether, 

 as is the case with a real butterfly. The impression is very beautiful 

 and fairy-like. These 'wings,' which are covered with gritty red 

 sand and lie flush with the surface of the ground, are generally about 

 an inch and a quarter square, the longest measurement being across 

 the front pair. If you insert the blade of your knife under the 

 smaller wings, you may turn the lid over its hinge, which is on the side 

 of the larger pair. This needs to be done carefully, for the lid is limp 

 and delicate and easily doubles up and loses it shape; the operation 

 is somewhat suggestive of tossing a pancake. You expose a smooth 

 bare spot, shaped like the double wings, nearly in the middle of which 

 is the hole. 



Though this butterfly lid is about an inch and a quarter square, 

 the hole is hardly, if anything, more than an eighth of an inch in 

 diameter. It is situated almost under the middle of the lid, just 

 below what corresponds to the thorax of the butterfly. The lid is 

 attached to the side of the hole towards the head of the butterfly, 

 and the attachment is restricted to the width of the thorax, leaving 

 the whole outline of the wings free. The hole, which is from two to 

 three inches deep and beautifully brown-webbed throughout, runs 

 straight into the ground at an acute angle under the hinge. The side 

 of the opening opposite the hinge slants, and on the slant, attached 

 to the web lining of the hole, lies a small, loose, felt-like flap. 



It must be remembered that 



~wv~, i...nn^ ^L...?l T , the large ' butterfly ' lid is never 



/ v=E - -' raised indeed, cannot be raised 



=W^I| by the spider ; for she is not strong 



^^f^ -P^fi enough, and, if she were, it would 



ijjBggdlj f Je^S^^s^ double up and lose its shape. So 



IJ Ill lJi tAp 1 ^ it always remains flat on the 



ground, covering the hole and the 



Median Section op Nest of New Trap- -, , , , , . , 



dook eresid. a-a>. Extent of lid across ground for more than half an inch 

 hole ; c-c, Extent of ' wings ' on each side all around it. The spider creeps 



of hole; A, Where hinge is affixed; B, -. , -, ., 



Flaps; a Blind side chamber. m and out underneath, as from 



under a blanket; you can trace its 

 passage by a little wave rippling along under the sand-covered wings. 

 The flap, I think, has two purposes. First, it affords the little 

 spider a means of easy ingress and egress to the hole under the lid; 

 it is firm and felt-like to give the spider a good hold for her feet 

 over the loose shifting sand, and it is slanting to enable her gradually 



