Answer: The beneficials you've purchased have been kept cool to fool them into thinking spring has just begun. Ladybugs, as you have discovered, are genetically programmed to disburse when they wake up from hibernation. If you have a large population of aphids, the ladybugs may stick around long enough to lay eggs before they fly away. When the eggs hatch the larvae will begin feeding on the aphids, so even though you don't see large numbers of adults around, they may have already worked their magic by laying eggs.
Wait a few weeks to see if you can find new populations of dark colored alligator-shaped ladybug larva. Check the undersides of leaves for clusters of orangish-yellow eggs, too. You may be surprised at what the ladybugs have left for you!
Note that most beneficial insects like disk- or ray-shaped flowers because the nectar in these flowers is easy to reach, so consider adding some cosmos, zinnias, and daisies to your garden to attract native beneficials.
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