The data on iNaturalist has obvious anthropocentric biases, but it can still be fun to contribute and analyze, example: https://www.inaturalist.org/observations/40799158 For six species of Papilionidae that live in Arkansas, it appears that annual die-off follows an exponential trend, see: https://0x0.st/iMzO.png
From the log-linear fits, the time constants are approximately: 15, 18, 21, 18, 25, and 22 days for glaucus, polyxenes, philenor, troilus, cresphontes, and marcellus respectively. I did not find reliable data about adult swallowtail lifetimes, did see 1-2 weeks or less or more. It could be that 20 days is a viable upper bound.
Yet this analysis is suggestive at best, possibly coincidental or biased. It would be interesting to look at a wider range of annual insects and see if exponential die-off is generally predictive of adult lifetime. Also, In many cases there's enough data to bin by day, and doing so can give a better idea of how many broods, etc. Glaucus, polyxenes, philenor, and marcellus all have prominent spikes during the last week of April. Is this species dependent or a consequence of more humans wanting to go outdoors? Does anyone else have ideas about how we can make good use of the data on iNaturalist (now up to 33M observations)? --Brad