Ptolemy didn't show any visible reaction to Lex's goading, but he was internally surprised by Lex's comments. Information about the Trelops was not exactly roadside knowledge, and to a certain degree, it was even kept hidden. This was because Trelops more often than not played a significant role in food production.
The human population was not small, with it being quite common for counties to have several billion humans. Even as organized as the Hum nation was, arranging for food at such a scale was a massive undertaking.
In the scenario they were facing, there were a few neighboring Trelops, with Karom being one of the weakest, and hence the most cooperative. Unfortunately, right after Karom's territory was that of another, extremely hostile and very aggressive Trelop.