From my layman understanding, animals that inject venom into the bloodstream by biting or poking are venomous. And ones that harm you when you eat them are poisonous.

Are there any animals (or plants) that fit both descriptions? 

I'm guessing eating a venomous rattlesnake will give you an upset stomach but not cause enough damage to be classified as poisonous. And I'm pretty sure poisonous tree frogs don't bite into their prey and inject them with anything. 

That is certainly an interesting question! 

First, to clarify definitions:

To be considered venomous the toxic substance must be produced in specialized glands or tissue. Often these are associated with some delivery apparatus (fangs, stinger, etc.), but not necessarily.

To be poisonous, the toxins must be produced in non-specialized tissues and are only toxic after ingestion.

Interestingly, many venoms are not poisonous if ingested.[1]

I know of at least three species that produce both poison and venom. One is a snake (although not a rattlesnake, which are, in fact, edible): Rhabdophis tigrinus, which accumulates toxins in its tissues, but also delivers venom via fangs.[2] The other two are frogs: Corythomantis greeningi and Aparasphenodon brunoi, which have spines on their snout that they use to deliver the venom.[3]


[1] Meier and White (eds.). 1995. Handbook of clinical toxicology of animal venoms and poisons. Boca Raton, Fla.: CRC Press, 477p.

[2] Hutchinson et al. 2007. Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus. PNAS 104(7): 2265-2270.

[3] Jared et al. 2015. Venomous frogs use heads as weapons. Current Biology 25, 2166-2170.
