Last August, Julia noticed a few holes in some string beans in the garden.
One of holes had droppings pouring out of it, and we could see someone fuzzy inside.
I opened this tunnel up for a better look at its inhabitant.
A quick look in a field guide told me what this was going to turn into, and I generally focus my rearing efforts on unknowns, but I decided to make an exception. After munching on beans for another week, it shed its fuzzy skin to reveal a fuzzy brown chrysalis.
In the spring, it emerged as a gray hairstreak (Lycaenidae: Strymon melinus) as expected. It obligingly posed on a dandelion before fluttering away.
We’re more than happy to sacrifice a few string beans to have these around.
BugTracks 
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In SE Arizona we’ve reared hairstreaks (I think – maybe blues, but still lycaenids) out of Astragalus pods, but the larvae were feeding on the inside of the pods, not on the beans. The beans were full of bruchids of a couple of different species.