(X 20.) order, showing affinities on the one hand with the Corrodentia (book-lice and biting lice) and on the other with the Hemiptera (cicads, bugs, &c.) .
Copeognatha: Corrodentia with delicate cuticle.
Mallophaga: Parasitic wingless Corrodentia (Bird-lice).
The Corrodentia retain vestigial maxillulae and two pairs of Malpighian tubes, but the wings are somewhat specialized in the Copeognatha and absent in the degraded and parasitic Mallophaga.
Orders: Dermaptera, Orthoptera, Plecoptera, Isoptera, Corrodentia, Ephemoptera, Odonata, Thysanoptera, Hemiptera, Anoplura.
In the absence of cerci the Corrodentia are more specialized than the Isoptera and Plecoptera, but some of them show a more primitive character in the retention of vestigial maxillulae - the minute pair of jaws that are found behind the mandibles in the Aptera.
A large proportion of the Corrodentia are wingless.
The name Corrodentia was first used by H.
Originally, however, the Corrodentia included the order which Enderlein has recently separated as Isoptera (see above).
As at present restricted, the Corrodentia include two distinct sub-orders.
CORRODENTIA: For Copeognatha see G.