Charles Ellicott Commentary Revelation 9:8

"And they had hair as the hair of women, and their teeth were as [teeth] of lions." — Revelation 9:8 (ASV)

And they had hair . . .—Translate, And they had hair as the hair of women, and their teeth were as the teeth of lions, and they had breastplates as iron breastplates; and the sound of their wings was as the sound of chariots of (having, i.e., drawn by) many horses, running to war.

The hair: It is said that some locusts are hairy, and the passage in Jeremiah (Jeremiah 51:27) has been quoted as evidence (the rough caterpillars described in that passage as “locusts bristling with hair”), but the application of the passage is uncertain. The rough caterpillar may be the locust in the third stage, when the wings are still enveloped in rough, horny cases that stick to their backs.

Others think the idea of the woman-like hair has its basis in the antennae of the locust. The teeth like those of the lion is a description whose origin is found in the prophet Joel, in his prediction of the locust plague: a nation comes upon my land, strong, and without number, whose teeth are the teeth of a lion, and he has the cheek-teeth (or, grinding-teeth) of a great lion. The terrible destructiveness of the locusts, and their strong, ceaseless, and resistless voracity, were thus described.

Their breastplates are taken as descriptive of their thoraxes, which in the vision seemed as strong as iron. The comparison of the sound of the wings to the thunderous sound of chariots and horses rushing into battle is repeated from Joel 2:5.