To-morrow will I bring the locusts - The word ארבה arbeh, a locust, is probably from the root רבה rabah, he multiplied, became great, mighty, etc.; because of the immense swarms of these animals by which different countries, especially the east, are infested. The locust, in entomology, belongs to a genus of insects known among naturalists by the term Grylli; and includes three species, crickets, grasshoppers, and those commonly called locusts; and as they multiply faster than any other animal in creation, they are properly entitled to the name ארבה arbeh, which might be translated the numerous or multiplied insect. See this circumstance referred to, Judges 6:5; Judges 7:12; Psalms 105:34; Jeremiah 46:23; Jeremiah 51:14; Joel 1:6; Nahum 3:15; Judith 2:19, 20; where the most numerous armies are compared to the arbeh or locust. The locust has a large open mouth; and in its two jaws it has four incisive teeth, which traverse each other like scissors, being calculated, from their mechanism, to grip or cut. Mr. Volney, in his Travels in Syria, gives a striking account of this most awful scourge of God: -
"Syria partakes together with Egypt and Persia, and almost all the whole middle part of Asia, in the terrible scourge, I mean those clouds of locusts of which travelers have spoken; the quantity of which is incredible to any person who has not himself seen them, the earth being covered by them for several leagues round. The noise they make in browsing the plants and trees may be heard at a distance, like an army plundering in secret. Fire seems to follow their tracks. Wherever their legions march the verdure disappears from the country, like a curtain drawn aside; the trees and plants, despoiled of their leaves, make the hideous appearance of winter instantly succeed to the bright scenes of spring. When these clouds of locusts take their flight, in order to surmount some obstacle, or the more rapidly to cross some desert, one may literally say that the sun is darkened by them."
Baron de Tott gives a similar account: "Clouds of locusts frequently alight on the plains of the Noguais, (the Tartars), and giving preference to their fields of millet, ravage them in an instant. Their approach darkens the horizon, and so enormous is their multitude, it hides the light of the sun. They alight on the fields, and there form a bed of six or seven inches thick. To the noise of their flight succeeds that of their devouring actively, which resembles the rattling of hail-stones; but its consequences are infinitely more destructive. Fire itself eats not so fast; nor is there any appearance of vegetation to be found when they again take their flight, and go elsewhere to produce new disasters."
Dr. Shaw, who witnessed most formidable swarms of these in Barbary in the years 1724 and 1725, gives the following account of them: "They were much larger than our grasshoppers, and had brown-spotted wings, with legs and bodies of a bright yellow. Their first appearance was towards the latter end of March. In the middle of April their numerous swarms, like a succession of clouds, darkened the sun. In the month of May they retired to the adjacent plains to deposit their eggs: these were no sooner hatched in June than the young brood first produced, while in their caterpillar or worm-like state, formed themselves into a compact body of more than a furlong square, and, marching directly forward, climbed over trees, walls, and houses, devouring every plant in their way. Within a day or two another brood was hatched, and advancing in the same manner, gnawed off the young branches and bark of the trees left by the former, making a complete desolation. The inhabitants, to stop their progress, made a variety of pits and trenches all over their fields and gardens, which they filled with water, or else heaped up therein heath, stubble, etc., which they set on fire; but to no purpose: for the trenches were quickly filled up and the fires extinguished, by infinite swarms succeeding one another; while the front seemed regardless of danger, and the rear pressed on so close that retreat was altogether impossible. In a month's time they threw off their worm-like state; and in a new form, with wings and legs, and additional powers, returned to their former voracity." - Shaw's Travels, 187, 188, 4th edition.
The descriptions given by these travelers show that God's army, described by the Prophet Joel, Joel 2:1-11, was innumerable swarms of locusts, to which the accounts given by Dr. Shaw and others exactly agree.