form of boron carbide. Dinies could chew iron. They
could masticate steel. They could grind up and swallow anything but
tool-steel reinforced with diamond chips. The same amateur chemist
worked it out that the surface soil of the planet Eire was deficient in
iron and ferrous compounds. The dinies needed iron. They got it.

* * * * *

The big dinies were routed by burning torches in the hands of angry
colonists. When scorched often enough, their feeble brains gathered the
idea that they were unwelcome. They went lumbering away.

They were replaced by lesser dinies, approximately the size of
kangaroos. They also ate crops. They also hungered for iron. To them
steel cables were the equivalent of celery, and they ate iron pipe as
if it were spaghetti. The industrial installations of the colony were
their special targets. The colonists unlimbered guns. They shot the
dinies. Ultimately they seemed to thin out. But once a month was
shoot-a-diny day on Eire, and the populace turned out to clear the
environs of their city of Tara.

Then came the little dinies. Some were as small as two inches in
length. Some were larger. All were cute. Colonists' children wanted to
make pets of them until it was discovered that miniature they might be,
but harmless they were not. Tiny diny-teeth, smaller than the heads of
pins, were still authentic boron carbide. Dinies kept as pets cheerily
gnawed away wood and got at the nails of which their boxes were made.
They ate the nails.

Then, being free, they extended their activities. They and their
friends tunneled busily through the colonists' houses. They ate nails.
They ate screws. They ate bolts, nuts, the nails out of shoes, pocket
knives and pants buttons, zippers, wire staples and the tacks out of
upholstery. Gnawing even threads and filings of metal away, they made
visible gaps in the frames and moving parts of farm tractors.

Moreover, it appeared that their numbers previously had been held down
by the paucity of ferrous compounds in their regular diet. The lack led
to a low birth rate. Now, supplied with great quantities of iron by
their unremitting industry, they were moved to prodigies of
multiplication.

The chairman of the Dail Committee on the Condition of the Planet Eire
had spoken of them scornfully as equal to mice. They were much worse.
The planetary government needed at least a pied piper or two, but it
tried other measures. It im