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Grasshopper is herbivore, spiders are carnivore. That is the difference right there.
Once I kept grasshoppers for months when I was a kid. It was quite easy. I kept them in a large glass jar. Every day, I went out to pick fresh grass for them. I released them after a few months.
For spiders, you need to catch live food for them.
I've also kept one for a few weeks before releasing it. It was actually in my house, and I caught it with a small paper box. I Fed it with live house flies. It seems to be very greedy on food, never stop catching the fly I put in there even it is already full.
Are you planning to keep ordinary small spiders or lets say those big tarantulas that can eat small rodents?
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