Mothra's larval form destroying the Tokyo Tower in the movie Mothra from 1961.
Apologies for the repeat but this topic came up today and I thought you'd enjoy
In the Fantastic Four comics Dr Doom was expelled from Empire State
University for carrying out 'Forbidden experiments'. The experiment in
question involved contacting the dead so maybe that's not that
surprising, but I was always amused by the notion that a University
might have a big list of 'Forbidden experiments'. Ah yes, item number
147, 'Contacting the Dead', right after number 146 'Reanimating the
Anyway, I was reminded of that when I took a quick look for some papers
on insect gigantism and came across this recent review paper Atmospheric oxygen level and the evolution of insect body size,
where they mention several experiments where people have selected for
insect gigantism over many generations under high oxgyen conditions in
The effects of hyperoxia on growth and body size are less consistent and often nonlinear (Harrison et al. 2009). Body size increases in the giant mealworm, Z. morio (27% O2; Harrison et al. 2009) and in the scarabaeid beetle C. texana (40% O2; Harrison et al. 2009).
I'm pretty sure 'Creating Giant Insects' would also have been on empire State's list. Did Mothra not teach us anything?
But the answer to our question of what other giant insect (and other arthropod) fossils have been found is:
Among insects, gigantism in the Permo-Carboniferous has also been
reported for Ephemeroptera, Diplura, Thysanura and the
extinct order Paleodictyoptera (Briggs 1985; Kukalova-Peck 1985). Arthropleura,
a group related to modern day millipedes, reached upwards of 2 m in
length, almost six times the size of any extant millipede.
So no, no Lepidoptera, you'll just have to make do with Mothra.