"Another of your precious little puzzles," Farrell said sourly. "I hope you enjoy unraveling it."

"Oh, we'll get to the bottom of it," Stryker said with assurance. "We'll have to, before we can leave them here."

They made a slow circuit of the lake, and the closer inspection offered a possible solution to the problem Stryker had posed. Chipped and weathered as the bones littering the mudflats were, their grisly shapings were unmistakable.

"I'd say that these are the bones of the older people," Stryker hazarded, "and that they represent the end result of another of these religio-economic control compulsions the Hymenops like to condition into their slaves. Men will go to any lengths to observe a tradition, especially when its origin is forgotten. If these people were once conditioned to look on old age as intolerable—"

"If you're trying to say that they kill each other off at maturity," Farrell interrupted, "the inference is ridiculous. In a hundred years they'd have outgrown a custom so hard to enforce. The balance of power would have rested with the adults, not with the children, and adults are generally fond of living.

Stryker looked to Gibson for support, received none, and found himself saddled with his own contention. "Economic necessity, then, since the valley can support only a limited number. Some of the old North American Indians followed a similar custom, the oldest son throttling the father when he grew too old to hunt."

"But even there infanticide was more popular than patricide," Farrell pointed out. "No group would practice decimation from the top down. It's too difficult to enforce."

Stryker answered him with a quotation from the Colonial Reclamations Handbook, maliciously taking the pontifical classmaster's tone best calculated to irritate Farrell.

"Chapter Four, Subsection One, Paragraph Nineteen: Any custom, fixation or compulsion accepted as the norm by one group of human beings can be understood and evaluated by any other group not influenced by the same ideology, since the basic perceptive abilities of both are necessarily the same through identical heredity. Evaluation of alien motivations, conversely—"

"Oh, hell," Farrell cut in wearily. "Let's get back to the ship, shall we? We'll all feel more like—"

His right foot gave way beneath him without warning, crushing through the soft ground and throwing him heavily. He sat up at once, and swore in incredulous anger when he found the ankle swelling rapidly inside his boot.

"Sprained! Damn it all!"

Gibson and Stryker, on their knees beside the broken crust of soil, ignored him. Gibson took up a broken length of stick and prodded intently in the cavity, prying out after a moment a glistening two-foot ellipsoid that struggled feebly on the ground.

"A chrysalid," Stryker said, bending to gauge the damage Farrell's heavy boot had done. "In a very close pre-eclosion stage. Look, the protective sheathing has begun to split already."

The thing lay twitching aimlessly, prisoned legs pushing against its shining transparent integument in an instinctive attempt at premature freedom. The movement was purely reflexive; its head, huge-eyed and as large as a man's clenched fist, had been thoroughly crushed under Farrell's heel.

Oddly, its injury touched Farrell even through the pain of his injured foot.

"It's the first passably handsome thing we've seen in this pesthole," he said, "and I've maimed it. Finish it off, will you?"

Stryker grunted, feeling the texture of the imprisoning sheath with curious fingers. "What would it have been in imago, Gib? A giant butterfly?"

"A moth," Gibson said tersely. "Lepidoptera, anyway."

He stood up and ended the chrysalid's strugglings with a bolt from his heat-gun before extending a hand to help Farrell up. "I'd like to examine it closer, but there'll be others. Let's get Arthur out of here."

They went back to the ship by slow