> Not sure about the first syllable of "poplitibus"
Lewis and Short doesn't mark that o short or long. This also occurred with vexo, which I assumed was because the first syllable of anything starting with vex- is necessarily long (because the 'x' is two non-liquid consonants).
In the case of poples, 'l' is a liquid and a short vowel could be revealed by the syllabification po-ples (or po-pli-), but I guess this is never attested? This verse can't answer the question because the syllable is allowed to be long.
or even determined to be long? The descriptions of the Alcaic strophe I found specify the first syllables of the first three verses as anceps but the first syllable of the fourth as long. Skimming the other odes in the third book, I havenʼt found another example where that would be doubtful. Maybe the hiatus candidates Trōica in 3:3, Pīeriō in 3:4, but fīet in a Sapphic strophe of 3:14 is certainly long.
But how is it long:
- probably not by position, because of muta cum liquida after the vowel. (An example for V.pl instead of Vp.l is capta virum puerosque ploret in 3:3.)
- the vowel length seems to be unclear, as indicated by Lewis / Short. I thought the etymology might help, but Walde / Hofmann tell that the etymology is unknown – and that a certain Muller Ait. W. 351 (?) is wrong to argue for a long o because it is clearly attested as short in verses by Accius and Lucretius.
Reading it like in school (with qualitative stress marking the quantitative meter), that would be:
Thanks for the link!