[jameshart]

I’m not sure what alternative strategy they are hypothesizing that would find shade more quickly, though?

it seems like the bugs have only one motor function - move in a random direction - and only one input sensor - temperature. What other strategies are available to them than random walk with a probability of movement based on a function of temperature and time?

[mhb]

I don't know either, but is it possible they are concluding that the bugs have only the function "move in a random direction" based on their observations?

If the bugs had the functions 1) move in one direction and 2) turn, then they might have observed a circular or spiral path.

[jameshart]

Put a blindfolded human in a zorb on an uneven patch of desert and I would be impressed if they could manage more than one bounce in the same direction in a row. Not sure what mechanism would enable a jumping bean to reliably bounce ‘forwards’.