About a week and a half ago, we had a couple of monarchs in the yard. We subsequently found over 150 eggs. Then a few days ago, we went looking for cats but only found a few and most of the eggs were gone. The only thing we can determine is it may be a black and orange bug (about 1/2 inch long) that is on the milkweed. What are they and is there any other explanation? We have been pinching as many of these bugs as we can, but they seem to be very prolific.
Some other possiblilities are ants and earwigs. I actually put a night-surveillance camera watching some eggs, and saw the earwigs patrolling each leaf of the milkweed. Some of the eggs I was watching were sucked dry, but I didn't see what ate them.