I am looking for a story I read in an anthology. In the story, the stars started to disappear and strange creatures appeared and collected all of the butterflies on earth. Eventually, the sun went out.
In the story, aliens had seeded the development of the Solar System, and had returned four billion years later to see how it turned out. A line of aliens appeared on the west coasts of all land masses and moved east, collecting all the butterflies. An entomologist is conscripted by the US army to find out why.
It turns out that they're collecting them because:
"Butterflies are the most beautiful thing on your planet, aren't they?"
"We are building...a place. Our leader wishes it to be a very special place. Therefore we are making it of these very special creatures."
At the same time as they were doing this, the aliens were also harvesting creatures from other planets:
"... Deep in the atmospheres of your four gas giants, Jupiter, Saturn, Uranus and Neptune, beautiful beings have evolved that...our leader treasures. On Mercury, creatures of quicksilver inhabit deep caves near the poles. These are being gathered as well. And there are lifeforms we admire that thrive on very cold planets."
The protagonist assumes that they're referring to Pluto, but later finds out that they mean to extinguish the sun and cultivate them on Earth.