My parents would mail order bricks of sleeping ladybugs. Put one in the garden and when they thaw out, they eat all the bad insects.

I always thought about putting one in someone's locker in high school, but never did it.

You can also do this with praying mantises, but they come as an egg nest. Put them under some leaves and a week or two later baby mantises everywhere eating all the bad things. After a couple months there's always a few big ones that stick around. Surprisingly intelligent and curious little things.

> fruitflies

careful with that one - there are interstate restrictions on transporting insects that are unrelated to the USPS.

There's no pre-existing market for "a bunch of stink bugs", however ladybugs are useful for non-toxic pest control (they'll eat aphids), so they can be ordered via mail.

Just because postal regulations permit them to be mailed does not preclude other reasons why that action might be illegal or expose you to legal liability.

There are lots of actions that are legal in isolation that become illegal when you do them to other people, particularly when done with malice.

Their spam mail and abuse of customers is malice.

Who is they?

... abuse of customers?

Digging up my residential address or sharing it with other businesses for any purpose other than to render services (e.g. to send a package that I ordered, you might need to share it with FedEx) is harrassment IMO.