8:16: "The dust became lice throughout all Egypt;" again, Exod.
8:17: "Smote dust...

it became lice in man and beast." Now the louse that infests the human body and hair has no connection whatever with "dust," and if subject to a few hours' exposure to the dry heat of the burning sand, it would shrivel and die.

But the tick is an inhabitant of the dust, a dry horny insect without any apparent moisture in its composition; it lives in hot sand and dust, where it cannot possibly obtain nourishment, until some wretched animal lies down upon the spot, when it becomes covered with these horrible vermin.

I have frequently seen dry desert places so infested with ticks that the ground was perfectly alive with them, and it would have been impossible to rest on the earth.
In such spots, the passage in Exodus has frequently occurred to me as bearing reference to these vermin, which are the greatest enemies to man and beast.

It is well known that, from the size of a grain of sand in their natural state, they will distend to the size of a hazelnut after having preyed for some days upon the blood of an animal.