72 
NOTE ON LEAF-FOLDING CATERPILLARS. 
T a piece of line thread ; the upper end is carried through a 
tiny hole pierced in the blade of the leaf close to one of the ribs R 
and is attached to a small piece of line wire at A ; the lower 
end of the thread similarly passes downwards through the 
surface of the leaf and carries a tiny cardboard pan suspended 
at W. 
Weights are cautiously added at W until the edge of the leaf 
E exactly touches the surface of the leaf resting on the block. 
The point of attachment A is then varied to A 1 and the 
weights adjusted as before. 
Proceeding thus, it was found — 
Point of attachment, at A, near centre of leal — 
Weight of pan-f-thread . . . . '2i gramme 
Added weight : — 
(i.) 4-2o gramme 
(ii.) 4*40 
mean 4'30 ,, 
Total Weight .. 4*31 ,, 
Point of attachment at Ag nearer end of leaf — 
Weight of pan-f-thread .. .. *21 gramme 
Added weight : — 
(i-) 2 -35 gramme 
(ii.) 2-40 
(iii.) 2*50 ,, mean 2 '42 ,, 
2-63 
Determination of breaking strain of thread. 
Advantage was taken of the fact that the larva, when alarmed, 
drops from the leaf by means of a thread. The larva is able to 
arrest its descent at will by seizing the thread just above the 
head by its front legs ; it ascends by rolling up the thread with 
its feet. 
It was easy to obtain a suitable thread for experiment by 
causing the larva to descend for the desired distance and then 
attaching to the extended thread a tiny paper pan by means 
of secotine ; the larva was then removed and the pan cautiously 
weighted until the thread broke. 
Proceeding thus, it was found :— - 
Breaking strain of single thread, 11 inches long-— 
Paper pan . . . . . . *075 gramme 
Added weight .... . . '070 ,, 
y) 
Total weight 
•145 
