1038 Marvels of the Universe 
Photo by] LW. Saville Kent. 
THE QUEENSLAND BARRAMUNDA. 
Also known as Dawson River Salmon. It measures about two feet in length. 
THE MAPLE-LEAF CUTTER 
BY EDWARD STEP, F.L.S. 
For many years we have all been familiar with the so-called Jumping Bean from America, which 
has at intervals aroused sufficient public curiosity to make it a marketable commodity in the streets 
of London. All the time we have had in our own fields and gardens quite as remarkable a natural 
curiosity of very similar character ; but the phenomenon has been—and up to the time of writing 
remains—unknown to all but a few naturalists. 
In the case of the “ Jumping Bean,” a seed with two flat sides and a convex side has been 
entered by a caterpillar, which feeds upon its substance and renders it useless as a seed. By some 
obscure action it is enabled to cause this seed to turn from one flat side to the other, this movement 
being the so-called jump. In the case under consideration, instead of a seed we have a circular 
disc cut out of the leaf of a Maple or Sycamore, and this disc moves about with short jerks in a 
startling fashion. The story of its fabrication we consider so interesting that we believe a brief 
recital of it will set numerous readers searching for the disc and its fabricator in their own neigh- 
bourhoods. 
We have already in this work given accounts of certain Saw-flies, but they are a numerous family 
and have not all the same habits. The propulsive power in what we will call the Jerking Disc is 
the grub of a Saw-fly. As usual with Saw-flies, its mother cut a slit with her saw in the leaf of a 
Sycamore or a Field Maple and deposited an egg in it. The egg hatches and the minute maggot- 
like grub that issues from it begins to excavate the juicy flesh between the upper and lower 
cuticles of the leaf. 
It does not share the devastating character of many of the Saw-fly tribe, who reduce many 
leaves to grim skeletons. In this case, at the end of his term of residence the Saw-fly grub has 
not consumed a fourth of the leaf-material, although he has succeeded in disfiguring the leaf with 
a yellow or brown blotch. The accompanying photographs of Sycamore leaves will make clear 
