Marvels of the Universe 1039 
the extent of this disfigurement. Sometimes there is only one Saw-fly grub at work in a leat, 
sometimes there are two or three, and occasionally four. The Sycamore leaf has five sharp-pointed 
lobes, and the grub always commences its operations at one of these points, and cuts away on all 
sides from that point, leaving an area behind him from which the green material has been com- 
pletely cleared. 
At last he appears to feel that he has eaten all that is necessary to enable him to work out the 
remainder of his destiny fasting. He now sets to work without compasses to describe a true circle 
in the upper cuticle of the leaf. With his jaws he makes a series of cuts, each one forming a segment 
of the circle, but separated from the next cut by a minute interval of unbroken skin. He finishes 
within the breadth of a pin at the point where he began, and the circle has taken nearly an hour 
to cut. 
The circle is complete, but it remains attached to the rest of the leaf much as a postage- 
stamp is attached to its fellows in a sheet of stamps. One can be removed from the centre of the 
sheet by a little pressure. The perforations in the leaf are short gashes instead of the dots of the 
stamp-sheet. 
Having all but separated his disc, our grub proceeds to weave a tissue of fine silk from the edges 
of the disc and beneath himself. This appears to us to be a remarkable piece of work, much more 
so than the weaving of the oval cocoon cleverly performed by the caterpillars of many moths. There 
the spinning is in all directions and the caterpillar can move as he pleases to effect it. In the begin- 
ning the caterpillar attaches threads to 
all available points to form an outer 
scaffold inside which he can fashion his 
egg-shaped cocoon with comparative 
ease. In the case of our grub, not one 
of his threads must extend beyond the 
cut edges of his disc, or his purpose 
would be defeated. The fabric to be 
woven is a flat tissue, and this part of 
the performance may be likened to a 
weaver lying in bed and weaving a 
complete bottom-sheet under his body. 
The grub is equal to the task ; and the 
next we know is that the disc has sepa- 
rated from the rest of the cuticle, and is 
now the upper side of a circular bag, the 
lower side being of closely-woven silk, 
and the grub lies snug between. How 
the separation from the leaf is effected 
is by no means clear. It has been sug- 
gested 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 com- 
plete severance of the disc from the rest ART 
of the leat cuts off so much of the SHY Showing the discoloured patch where the Leaf-cutter is still at work. 
of moisture that the disc contracts and ~The long dark mark in the upper part of the light patch is the larva 
so effects complete severance. mache die Iba! eutiets: 
Photo by) (1. Main, PES. 
