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About 6 cm long, color black, one horizontal white line over the back, hind legs with a structure that looks as leaf, Hemiptera.
Garden of a house.
Leptoglossus for sure, but I am not sure if Phyllopus is really found in Costa Rica. There are many other species there.
Following up on asergio's ID, the very straight white line tell me it's Leptoglossus phyllopus, that is I'm assuming it occurs in Costa Rica. But since it is a southern US bug (also south west) it probably does extend throughout Central Amer.