"There could be a hundred colonies on this planet without any one knowing of any other. I can only guess about your robots, but I suspect they ran into sphexes."
Roane paused, with his fork in his hand.
"I read up on this planet, since I was to report on its colony. A sphex is part of the inimical animal life here. Cold-blooded belligerent carnivor, not a lizard but a genus all its own. Hunts in packs. Seven to eight hundred pounds, when adult. Lethally dangerous and simply too numerous to fight. They're why no license was ever granted to human colonists. Only robots could work here, because they're machines. What animal attacks machines?"
Huyghens said:
"What machine attacks animals? The sphexes wouldn't bother robots, of course, but would robots bother the sphexes?"
Roane chewed and swallowed.
"Hold it! I'll agree that you can't make a hunting-robot. A machine can discriminate, but it can't decide. That's why there's no danger of a robot revolt. They can't decide to do something for which they have no instructions. But this colony was planned with full knowledge of what robots can and can't do. As ground was cleared, it was enclosed in an electric fence which no sphex could touch without frying."
Huyghens thoughtfully cut his food. After a moment:
"The landing was in the winter-time," he observed. "It must have been, because the colony survived a while. And at a guess, the last ship-landing was before thaw. The years are eighteen months long here, you know."
Roane admitted: