Why does only the Septuagint mention a swarm of locusts coming from the east? and, the one caterpillar, king Gog?
Let's start with the MT:
כֹּ֤ה הִרְאַ֙נִי֙ אֲדֹנָ֣י יְהוִ֔ה וְהִנֵּה֙ יוֹצֵ֣ר גֹּבַ֔י בִּתְחִלַּ֖ת עֲל֣וֹת הַלָּ֑קֶשׁ וְהִ֨נֵּה־לֶ֔קֶשׁ אַחַ֖ר גִּזֵּ֥י הַמֶּֽלֶךְ׃
Literally this says:
This is what the LORD showed me The LORD is going to form locusts At the beginning of growing the leqesh And Look the leqesh [is] after the mowings of the king.
Here, I have not translated the mysterious leqesh.
So this doesn't make sense, and most scholars believe that the last sentence is a scribal addition to try to explain the hapax legomenon leqesh - לָּ֑קֶשׁ:
The purpose of the later addition in v. 1b* was to define לקשׁ (“late-planting”) more precisely. It was probably this addition which introduced the cumbersome link with v. 2* formed by the first two words thereof. והיה (“and it will be”) is inappropriate as a continuation of the report (cf. the beginning of 7:4b*, and see above p. 280, on 6:9*) and has therefore been considered a misspelling of וַיְהִי (so Joüon, par. 119z). The conjunction אם (with a following perfect) seems equally strange in light of the otherwise paratactic style. Thus as the original continuation of v. 1a*, preceding the introduction of the prophetic speech, we should expect a simple וְכִלָּה (“when he had finished”), corresponding to the form ואכלה (“and it devoured”) in 7:4b* before 7:5*. The perfect states the fact which elicits the prophet’s objection. Less in keeping with the style of the parallel second report is the proposal to restore וַיְהִי הֻא מְכַלֶּה (Charles Cutler Torrey [“On the Text of Am 5:25*; 6:1*, 2*; 7:2*,” JBL 13 (1894): 63], Wellhausen, Sellin, and others). Wolff, H. W. (1977). Joel and Amos: a commentary on the books of the Prophets Joel and Amos. (S. D. McBride, Ed.). Philadelphia: Fortress Press.
So Let's look at the other witnesses:
This is what the Lord God showed me: behold, a formation of locusts at the beginning of the sprouting of the later crop; and behold, it was the [young shoots] after the king’s [early crop was cut].
Here, the targums, together with the Syriac and the LXX interpret yṣr as a noun yēṣer ("formation") instead of MT yôṣēr (“one forming”). But the Vulgate agrees with the MT.
Next, the targums replace MT ‘lwt ("growing") with ṣmwḥ ("sprouting").
Finally, the targums diverge completely with MT to try to explain the last sentence, but this is much more sensible (to me).
- Syriac (from Bible Hub):
Thus showed me The Lord of Lords: a creation of locusts at the beginning of growth of late grass and that late grass after the mowing was the King’s
That's a little better, but is it from an accurate vorlage? We don't know.
- Let's look at LXX (LES):
Thus the Lord God showed me and behold, the offspring of locusts is coming early, and behold, one locust is Agag, the king.
Brannan, R., Penner, K. M., Loken, I., Aubrey, M., & Hoogendyk, I. (Eds.). (2012). The Lexham English Septuagint (Am 7:1). Bellingham, WA: Lexham Press.
The differences appear to be that the Hebrew vorlage that the LXX is based has יֶלֶק (cf. Joel 1:4*, “locust”) instead of the enigmatic לקשׁ and אֶחָד instead of אחר, and גּוֹג instead of גזי.
But again, is this vorlage accurate? These are all plausible substitutions, but which is the correct version?
So at the end of the day, the MT is mangled and there is disagreement by the other witnesses on what the true vorlage should be, so Bible translators are left with some tough choices. Unfortunately the Dead Sea Scrolls don't help.
Here is Hermeneia's translation of Amos 7.1-3, which is as good as anyone else's:
Thus [the Lord] Yahweh showed me:
There was someone forming a locust-swarm, just when the late-planting had begun to shoot up, and [here late-planting (is that which) follows the king’s mowings, 2/ and when] it was about to finish off the herbage of the land completely, I said: “My Lord Yahweh, do forgive!’How is Jacob to endure? For he is so small.” 3/ Then Yahweh repented concerning this. “it shall not happen,” Yahweh said. Wolff, H. W. (1977). Joel and Amos: a commentary on the books of the Prophets Joel and Amos. (S. D. McBride, Ed.) (p. 292). Philadelphia: Fortress Press.
1Cathcart, K. J., McNamara, M., & Maher, M. (1990). Editors’ Foreword. In K. J. Cathcart, M. Maher, & M. McNamara (Eds.), K. J. Cathcart & R. P. Gordon (Trans.), The Aramaic Bible: The Targum of the Minor Prophets (Vol. 14, Am 7:1). Collegeville, MN: The Liturgical Press.