Stink bugs, leaf footed bugs, and assasin bugs are all closely related hemipterans found across the U.S. and share a similar body shape. Stink bugs are a little wider towards the head (like the one in Hedge's photos), while assasin bugs and leaf footed bugs have the same shape, but a longer body. To tell those 2 apart, you just need to look at the legs, as leaf footed bugs have that wide leafy structure (like in Sue's photo) while assasin bugs do not (although juveniles do not have this and they are very hard to tell apart at that stage). Both stink bugs and leaf footed bugs feed on plants while assasin bugs eat other bugs. All 3 have a piercing, sucking mouthpart for feeding and at least stink bugs and leaf footed bugs exude a very bad smell...an assasin bug also (only if picked up) can give a pretty painful bite. I've attached a pic I took while in Madagascar of a tropical assasin bug, you can see its tube-like mouthpart pretty well
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Sara