By Harry Pettit  Unarmed but ready for actionChristine MillerSpecies: Leaf-footed cactus bugs (Narnia femorata) Habitat: prickly pear cacti around the southern US and Central America Silver linings can be hard to come by, but for the leaf-footed cactus bug – who appear to grow larger testes in response to losing their sparring weapons – life could...