The spathe has rotated close to 20 degrees to the left.  Although no female flowers have ever been present in any photograph, they are there!  The explanation as to why we cannot see them is found later on this page.  It is not strongly evident but the pheromone has begun to return as has the heat of thermogenesis   The scent has changed somewhat and the mint smell is no longer apparent.  All that is now noticed is a musky smell.  Both my wife and oldest daughter could easily detect both the heat and the pheromone.  To detect the heat all that was necessary was to hold a flattened palm in front of the spathe without touching any part of the inflorescence.

French aroid pollination researcher and expert Marc Gibernau has stated the spathe and spadix lie at an angle of approximately 45 degrees to the vertical for a purpose.  The angle is more effective for the heat of thermogenesis to be dissipated along with the spadices' pheromones into the air of the rain forest night.   Notice what occurs in the next photograph.
 

6:30PM

The spathe has now rotated to a 45 degree angle on the axil in to increase the effects of thermogenesis.  It also appears to be slightly closing.  I have read in some material the spathe actually closes around the beetles and they do the work of pollination inside the closed tube.  However, Julius offers a better explanation below.  The pheromone is now only slight and no heat from thermogenesis can be felt on the hand.  The scent is of a slight musk combined with a small amount of mint.  Again, no female flowers can be observed but the explanation follows.

From Dr. Tom Croat, "the receptivity of the female flowers is short once the spathe is open.  They are protogynous, of course, like most Araceae but also promptly timed to be receptive only at anthesis on the first night of flowering.  This prevents self pollination."

In botany protogynous relates to a flower in which the stigma is receptive prior to the pollen being shed from the anthers of the same flower.

And from Julius Boos:  The blooming/anthesis cycle of this species lasts 2 days.  The lower portion (the tube) of the spathe never opens in this species, probably in the entire genus.  I do not believe that this spathe could trap the Scarab beetle pollinators even if it wanted to as they are strong animals.   I once collected about a dozen of them from a bloom in the jungle of E. Ecuador, and was unable to ''hold on'' to them for long as they would burrow (painfully, I may add!) between my fingers and out of my tightly closed fist.

You could take notes and observe if the constriction around the spadix opens, then closes and then opens again when the next bloom goes through its cycle, measurements taken at the ''waist'' and visual observations would tell you if this is happening.  Read pg. 59 of Deni`s book.  Her details esplain a lot about this event there.  I do not believe the beetles need to be 'trapped' by this closing, they could and would escape at any time if they wanted to, but why would they??   Warmth, food (they will eat the sterile flowers as a snack) and lots of partners and sex in a secure ''room'' are being provided, so why would they even want to leave? Perhaps the closing of the spathe at the constriction may retain the heat in the lower portion of the spathe tube for the beetles.  When the warmth stops at the end of the cycle, and the food is used up, they just crawl out  picking up pollen on their now resin-covered legs and bodies and fly off to the next available ''ready'' bloom.

By the way, I believe that some sting less bees collect this resin and use it in the construction of their combs/cells and in waterproofing of their nests.  Native Indians in South America collect it from their nests and use it to make their blow guns both air and watertight."