Large Milkweed Bug Explosion

I had been wondering about the pristine condition of my milkweed plants: No monarch caterpillars, no aphis nerii, no milkweed bugs large or small.

Then a few days ago, a few Oncopeltus fasciatus adults appeared on milkweeds and plants near them in the back yard. One pair was mating on the milkweed flowers. Other individuals were just hanging out.

Two days later, I found a milkweed plant covered with mating pairs; I counted 20 individuals at one point. Other nearby plants had adult bugs on them, too. I looked for eggs on the pods but so far didn't see any. Eggs are laid in or on the seedpods, since the milkweed seeds are the food for the nymphs (and adults).

The females are said to lay about 2000 eggs in their lifespan so I figure it won't be long before the population of Large Milkweed Bugs spreads through the milkweeds in the backyard, onto the plants in the front and beyond onto my neighbors' milkweeds, eventually forming the clumps of bugs (aggregations) that hunker down in the leaf duff on cooler autumn or winter nights. I think in colder climates the adults overwinter but here in mild southern California all stages are able to survive the winter as long as there is something to eat.

Why these bugs have gone missing this spring and early summer on my milkweed: I don't know.