"Simply that they aren't," said Ned.
"What are they, then?"
"Flies."
"Well, what is a small fly but a gnat?"
"And what is a gnat but a small fly?" added Charley.
"The two are not at all the same thing," answered Ned. "That is a popular mistake. I have heard people say they could stand mosquitoes, but couldn't endure gnats; and yet the mosquito is a gnat, and what these people call gnats are not gnats at all, but simply small flies."
"What constitutes the exact difference?"
"The shape of the body. All flies are two-winged insects, and gnats are flies in that sense, of course; but gnats are those flies that have long bodies behind their wings, to balance themselves with. Mosquitoes are our best example of them. These sand flies, you see, have very short bodies."
"Yes, but very long bills, I fancy," said Charley.
"Well," said Jack, "all that is news to me."