TAILORS 203 



tion from the leaf is effected is by no means clear. 

 It has been suggested that it is due to the pull of 

 the silk threads beneath ; but this can scarcely be 

 so, as the silk floor sags slightly in the middle, which 

 indicates that it is not taut, whilst the vegetable 

 roof is flat. Our own theory is that the almost 

 complete severance of the disc from the rest of the 

 leaf cuts off so much of the supply of moisture 

 that the disc contracts and so effects complete 

 severance. 



You may be looking at one of these discs, still in 

 position on the leaf, when suddenly it separates 

 and drops to the ground. The disc, if it has 

 alighted on an unsatisfactory spot, begins to move 

 about with shuffling jerks, apparently due to the 

 grub taking hold with its hind body and suddenly 

 jerking the bulk of its body to one side. Judging 

 from the fact that the way to induce these move- 

 ments is to expose the disc to strong sunlight (or 

 electric light) they appear to be a provision against 

 the grub getting dried up. It seeks a shady, moist 

 position, where it can lie safely all through the 

 autumn and winter. Not until spring does it 

 change into a chrysalis in its cell, and a little later, 

 when the maple and the sycamore are in leaf, a 

 four-winged Sawfly emerges, and sets about pro- 

 viding for the continuance of the race. > 



So far we have considered tailors that rely entirely 

 or partly upon materials they have adapted to 

 their use. We have now to glance at a group 

 which construct clothing from the waste products 



