Joel 2:4

as the appearance of horses, &c. partly on account of their speed and compact array, but chiefly on account of a resemblance which has been often observed between the head of a locust and the head of a horse (hence the Italian name cavalletta, and the German name Heupferd). Theodoret says, "If you observe attentively the head of a locust, you will find it exceedingly like the head of a horse." And an Arabic poet, quoted by Bochart, Hieroz. Pt. II., L. iv., c. 4, writes, "They have the thigh of a camel, the legs of an ostrich, the wings of an eagle, the breast of a lion, a tail like a viper's; and the appearance of a horse adorns them about the head and mouth." C. Niebuhr heard a similar description in Bagdâd (Beschreibung von Arabien, 1772, p. 173). "To this day the same metaphor is familiar in every Arab camp" (Tristram, N.H.B[36] p. 314). See also Revelation 9:7.

[36] .H.B.… H. B. Tristram, Natural History of the Bible(1868).

as horsemenor, possibly, as war-horses so do they run charging with the same directness, and also with the same swiftness and sure-footedness. For these virtues of an ancient warrior, cf. 2 Samuel 1:23; 2 Samuel 2:18; Psalms 18:33.