what is smaller, a louse or a gnat?

I have thbis book that has the sizes of insects.

A Fungus Gnat is 1/8 to 1/4 inches (3 - 6 mm).
Another species of gnat, the Bodega Black Gnat, is 1/16 to 1/8 inches (1 - 3 mm).

As for lice, a Chewing Lice is 1/16 to 1/4 inches (2 - 5 mm) long.
Hog Lice are 1/4 inches (5 - 6 mm).
Human Body lice is 1/8 inches (3 mm).

So it really depends on the species.

Is that helpful? Anything else you'd like to know about the specific species. There's lots mroe information on them in here.

P.S. the question could go in the biology or zoology sections over the pets section.

Errr, all those insects were taken from the Field Guide to North American Insects and Spiders so I doubt they'll help in your trivia question because it's about biblical times and all.