Note 12 — Chapter XII
Reading edition
Lubbock considers that Papirius should be placed in a distinct family from Smynthurus, because it wants tracheæ. Their presence or absence scarcely seems to us to be a family character, as they are wanting in the Poduridæ, and are not essential to the life of these animals, while in other respects Papirius seems to differ but slightly from Smynthurus.