An antenna or transmission line has resonances at (or near) odd
harmonics. But a lumped LC circuit doesn't. A bugcatcher is a
combination of the two. I'd think it likely that it has multiple
resonances, but not at harmonically related frequencies.

If you want a rule of thumb, don't look for harmonically related
resonances in any antenna containing a significant amount of lumped L or
C, or L and C distributed over a relatively small distance.

Roy Lewallen, W7EL

Zack wrote:

"It" refers to the balun, not the antenna. The balun works on odd, but
not even harmonics. Anyone have a simple explanation for explaining
whether something will work on harmonics or not? For instance, how do
you explain that a 40M bugcatcher won't exhibit a 15m resonance?

Zack Lau W1VT