1938] 
Lines of Descent of Insects 
171 
metabola or Neuropteradelphia) ; and the Orthopteroid 
insects represent the ancestral types of the group as nearly 
as any known forms. The Orthopteriod insects were ap- 
parently not derived directly from the Palseodictyoptera, 
but were probably derived from the Palseodictyopteran 
stock by way of Synarmoge (or Synarmogoge as it is some- 
times spelled). Since only a fragment of one wing of 
Synarmogoge is known, however, all that can be said con- 
cerning it is that it exhibits certain characters intermediate 
between the Palseodictyoptera and the Protorthoptera. 
The Protorthoptera, shown at the base of the lines of de- 
scent of the higher insects in the accompanying phylogenetic 
tree, include the Protoblattids (which have a demarked 
claval region in the fore wings) as well as the Protorthoptera 
in the narrower sense (which have no demarked claval 
area), since the Protoblattids and Protorthoptera merge so 
indistinguishably that they may be combined into a single 
ancestral group from which all of the higher insects were 
ultimately derived. The Protoblattids are the most primi- 
tive representatives of the group, and are more like the 
direct ancestors of the Blattids, Mantids and Isoptera, while 
the other members of the Protorthoptera are somewhat 
closer to the direct ancestors of the Orthoptera. 
The Orthopteroid insects are characterized by the fact 
that the cerci are well developed and the parapodial plates 
(paraprocts) are distinct in all of the members of the group. 
An anal fan is developed in the hind wings of most of the 
Orthopteroid insects, but in some of them, such as the 
Embiida and Isoptera (excepting Mastotermes) the wings 
are secondarily homonomous. The Orthopteroid insects 
have been grouped into three superorders called the 
Panorthoptera (or Orthopteria) , the Panplecoptera (or 
Plecopteria) , and the Panisoptera (or Isopteria). 
The superorder Panisoptera (Isopteria) includes the 
Palseoptera (Blattids and Mantids) and the Isoptera, and 
is characterized by the fact that the lateral cervical sclerites 
are contiguous in the midventral line, the mesothoracic 
trochantins do not unite basally with the episternum; a 
claval area is usually demarked in the fore wings, and the 
seventh abdominal sternite projects below the ovipositor in 
the members of this superorder. The Blattids have pre- 
