Almost certainly the heat.
Maybe it's like a pleasant warmth from within and they just fly towards the direction of increasing warmth. I guess it wouldn't take many dBms of absorbed power to slightly heat a wasp.
I remember treatments like these happened in GP's offices in the 1980s.
The animal equivalent to an IRB is usually an Institutional Animal Care and Use Committee (IACUC), but the laws they are subject to vary with jurisdiction, and their use is optional if your grant provider (i.e. NIH) or academic publisher do not require them.