Male squash bees choose to sleep/rest in pumpkin/squash flowers. Perhaps the microclimate within wilting flowers provides temperature cues to male squash bees that make the flowers attractive and cause the male bees to become more sedate.
I think the USDA maintains some sort of index of who is doing what in Agricultural research in the US. However, in my experience such lists are quite incomplete.
As you undoubtedly know beetles were the first pollinators, so beetle-flower interactions might go back to a time near the emergence of angiosperms.
We are now starting some measurements of temperatures in the flowers and throughout the lives of the reproductive parts of plants (floral buds to fruiting structures). Just for interest I took some temperatures in some Nigella follicles (are they?) that form bladder like structures. In sun shine, about 3 C warmer than surrounding air. We also have data accumulating on the interior temperatures of the syncalyces of Physalis peruviana. Those are also a few degrees warmer than the surrounding air.