174 
Psyche 
[December 
Fsocoptera. The Anoplura were probably derived from 
ancestors closely allied to the Mallophaga; and all of these 
insects are sometimes grouped together as Corrodentia, 
although they are apparently worthy of ordinal rank. 
The mouthparts of the Thysanoptera (which have distinct 
maxillary and labial palpi) are much more primitive than 
those of the Hemiptera, and it is possible that the Thysanop- 
tera were descended from a slightly more primitive type 
than the Hemiptera were. At any rate, the Thysanoptera 
were apparently descended from Protorthopteroid ancestors 
very closely related to those from which the Hemiptera were 
derived, and these ancestors evidently resembled the Psocop- 
tera very closely. The Hemiptera were evidently descended 
from the same Protorthopteroid ancestors from which the 
Fsocoptera were derived, and the Psocoptera have departed 
the least of any living insects from the types ancestral to 
the Hemiptera. Not only does the venation of living 
Psocoptera parallel that of certain Hemiptera-Homoptera 
strikingly closely, but the venation of certain fossil Hemip- 
tera merges with that of certain fossil Psocoptera so in- 
timately that there can be no doubt that the two groups had 
a common Protorthopteroid ancestry; and the fact that 
many Hemiptera have a claval area demarked in their fore 
wings may possibly indicate that their Protorthopteroid 
ancestors resembled Protoblattids (in which the claval area 
is also demarked) in some respects. At any rate, the 
Hemiptera could not possibly have been derived from such 
Palseodictyopteroid insects as Eugereon (mistakenly called 
“Protohemiptera”) , since Eugereon belongs in the section 
Palaeopterygota, whose members are incapable of laying the 
wings along the body in repose, while the Hemiptera were 
evidently descended from ancestors capable of laying the 
wings back along the body in repose, and the venation of 
primitive Hemiptera does not bear the slightest resemblance 
to that of Eugereon. 
Some Parametabola (Hemipteroid insects) parallel the 
Holometabola remarkably closely in their method of devel- 
opment, and indicate very clearly that complete meta- 
morposis arose through an increasing divergence between 
the immature and mature forms (rather than through the 
precocious emergence of “free-living embryos”, as certain 
