Monarch eggs on milkweed pods

We were in the front yard yesterday when a Monarch sailed by.  She was touching down on various leaves, so we knew her mission was ovipositing rather than nectaring.  Then she did something unusual - rather than deposit the egg underneath a leaf, she placed it on a milkweed pod [in the image the egg is the upper, cream-colored sphere; the lower white blob is sap from the broken stem at right].  And again:

After she few away we searched the milkweed pods in the front garden and found 3 more eggs.  This was an interesting variation for us to encounter, because the archetypal location for Monarch eggs is on the underside of leaves (see here, and here).

In point of fact, the eggs are probably better camouflaged on the spiky pods than on the smooth leaves, but the other factor may be that at this time of year (mid-August), most of the leaves on the milkweed are mature and somewhat leathery in texture.  The newly-forming pods may provide a more tender food source for the emerging first instars.

The caterpillars that emerge from these eggs, should they survive to adulthood, will then fly to a valley in northern Mexico where their ancestors spent last winter.  The mind reels.