In Exodus 4:4, when Moses seizes the rod-turned-serpent by its tail, this signifies that law of God can raise up the lowest, most sensory parts of our nature. (Arcana Coelestia 6952)

Tail here also signifies persuasive sensuous knowledges. (Apocalypse Explained 559, Doctrine Regarding Sacred Scripture 13)

'Tail' signifies the opposite extreme of the head, because the brain is continued to the tail through the spine, This is why the head and tail make one, as the first and last. Where 'head' signifies faith alone justifying and saving, 'tail' signifies everything that confirms that belief, taken from the Word, and so the truths of the Word are falsified.... Because a 'tail' signifies the extreme, and so it is the sum or aggregate, Jehovah told Moses to 'take the serpent by the tail, and he took it, and it became a rod,' in Exodus 4:3-4. This is also why they were commanded to 'take off the whole tail near the backbone, and sacrifice it together with the fat of the entrails, kidneys, intestines, and liver,' as in Leviticus 3:9-11, 8:25, 9:16, and Exodus 29:22. 'Tails' signify sensory knowledge, because the tails of animals are continuations of the spine, or spinal cord, which contains the base of the cerebrum, which signifies intelligence and wisdom. The low extremes of intelligence and wisdom are sensory knowledge.

(Odkazy: Apocalypse Revealed 438; Exodus 3, 4:3; Revelation 9)

438. They had tails like scorpions. (9:10) This symbolizes the Word's truths falsified, by which they induce a mental numbness.

A tail symbolizes the last extension of the head, because the brain extends through the spinal column into the tail. Consequently the head and the tail are united as their first and last elements. Consequently, when the head symbolizes a justifying and saving faith alone, the tail symbolizes in summary all its proofs, and as these are taken from the Word, it symbolizes the Word's truths falsified.

Everyone who assumes some principle of religion on the basis of on his own intelligence and puts it at the head of the rest, also takes proof passages from the Word and puts them at the tail, thus inducing a mental numbness in others and so doing them injury. That is why we are told that "they had tails like scorpions," and next, that "there were stings in their tails," and that "their power was to hurt men." For a scorpion symbolizes a persuasiveness that induces a numbness in the intellect (no. 425).

To be assured that the tail is an extension of the brain through the spinal column to its final point, ask any anatomist and he will tell you. Or look at a dog or some other fierce animal that has a tail, and if you treat it kindly and make yourself agreeable to it, you will see its stiffened back soften and its tail move in a corresponding manner. But on the other hand, if you annoy it, its backbone stiffens.

[2] The primary tenet of the intellect that is assumed as a principle is symbolized by the head, and its final expression by the tail, also in the following passages:

...He will cut off head and tail from Israel... The elder and honorable man is the head; but the prophet who teaches lies is the tail. (Isaiah 9:14-15)

There will not be any work for Egypt that the head or tail... may do. (Isaiah 19:15)

Nothing else is symbolized by the dragon's seven heads and the tail by which it drew a third of the stars of heaven and threw them to the earth, in Revelation 12:3-4; and also by the tails like serpents, having heads, with which they do harm, in verse 19 of this chapter.

Since the tail symbolizes the final element, and the final element embraces all the rest, therefore Jehovah said to Moses,

"...take (the serpent) by the tail." And he... caught it, and it became a rod... (Exodus 4:3-4)

The priests were also commanded therefore to remove the whole tail close to the backbone and to sacrifice it with the fat on the entrails, the kidneys, the intestines, and the liver (Leviticus 3:9-11; 8:25; 9:19, Exodus 29:22).

To be shown that the final element contains and embraces all the prior ones, see The Doctrine of the New Jerusalem Regarding the Sacred Scripture, nos. 38 65, and Angelic Wisdom Regarding Divine Love and Wisdom, nos. 209-216 217-222.