Terumos, Chapter 10, Mishnah 9. This mishnah also deals with the laws of pickling, this time with pickling locusts. The Torah lists four kosher species of locust, while all other species are not kosher.
It is worth noting: all the creatures of this family are called chagavim (locusts). When they multiply in dense concentrations and food is plentiful, they become agitated and begin to migrate in swarms, and then they are called arbeh - but it is the very same creature.
The question addressed in the mishnah:
The case is one of pickling kosher and non-kosher locusts together, and the question is whether the flavor released by the non-kosher locusts will be absorbed by the kosher ones and render them forbidden, as we saw in the previous mishnah regarding kosher and non-kosher species of fish.
The unique nature of insects:
With locusts the situation is different. Insects, like all arthropods, have no blood. They have an open circulatory system, and the fluid that comes out of them is not red but greenish. This fluid does oxygenate their bodies, but it does not contain the hemoglobin found in ours - that iron-based molecule whose color is red. Scientifically it is called hemolymph, and its color is green when oxygenated.
Chazal too noticed this point, and held that any fluid found inside a locust, as in other creeping creatures, is nothing more than general moisture and is not part of the locust itself.
The wording of the mishnah:
"Chagavim temei'im shenichbeshu im chagavim tehorim - lo paslu es tziram" - the brine, the salt water in which the locusts were pickled, is not forbidden at all, because any fluid squeezed out of the non-kosher locusts is nothing but waste and mere moisture.
"He'id Rabbi Tzadok al tzir chagavim temei'im shehu tahor" - the juice that comes out of non-kosher species of locust is entirely pure and permitted.
The difference between the opinions:
The Tanna Kamma: there is no possibility, even hypothetically, of drinking a locust. The fluid squeezed out of it is not fit for drinking on its own, but in a mixture it does not render the mixture forbidden.
Rabbi Tzadok: the fluid itself, though repulsive, has the status of licking sweat off a person's face - there is no prohibition in it at all and no need to be concerned about it, since it is not part of the creature's body.
The halachah: The halachah follows Rabbi Tzadok, that any foul liquid squeezed or pressed out of locusts, even from locusts that are not kosher, is not considered like the locust itself, and therefore it is not forbidden.