Answer: It's a real zoo out there on your cherry trees! The white spiders are Crab Spiders, members of the hunting spider family (Thomisidae). Spiders are considered beneficial in the garden because they prey on small insects. I'd encourage the spiders to live wherever they want to in the garden, knowing they will be consuming quantities of insects.
Aphids come in all colors and sizes. The black bean aphid fits the description of the aphid you're finding on the leaves of your cherry trees. Aphids are sucking insects and large populations can damage the leaves, making them pucker and curl. When aphids feed, they excrete a sticky substance called honeydew. This excrement is just high enough in sugar to promote the development of a blackish fungus. That's probably why you're seeing a blackish color on the leaves.
The third insect, the one found inside the curled leaves, sounds like lady beetle larvae. They're dull black, alligator shaped, with what looks like spines on their backs. These are positively one of the most beneficial insects in the garden. They consume countless numbers of aphids each day. So, it sounds like the aphids have attracted benefical lady beetles and hunting spiders.
With this natural balance of good insects and bad insects, you shouldn't have to do anything at all - the bug problem will resolve itself.
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