34 
Psyche 
[February 
sideration, it would appear to be more probable that instead 
of arising from Eugereon, the line of descent of the Homoptera 
arose at the base of a common Protorthopteron-Protoblattid 
stem, or it parallels the common Protorthopteron- Protoblattid 
stem very closely as we trace them all back to their common 
ancestors resembling the Palseodictyoptera, which gave rise to 
such forms as Eugereon, and the Megasecoptera. 
In the nature of their mouthparts, their widely separated 
coxae and broad sterna, and to some extent in the nature of their 
ovipositors, etc., the Thysanoptera exhibit many features sug- 
gestive of a relationship with the Hemiptera; but the venation 
of the Thysanoptera is too highly specialized to be of much 
value in determining the origin and affinities of the Hemiptera, 
although they do offer certain points of contact with both 
Hemiptera and Psocids, which would be expected if the Psocids 
and Hemiptera were related both to each other and to the 
Thysanoptera. The character of the radial and median veins 
which extend parallel to each other down the center of the wing 
of the Psocid shown in Fig. 17 is very suggestive of the character 
of the radius and media which also extend parallel to each 
other down the middle of the Thysanopteron wing shown in 
Fig. 15. The radial and median veins of the Orthopteron shown 
in Fig. 16, however, likewise extend parallel to each other down 
the center of the wing, and the character of the cubital vein, 
and the branches of the radial vein of the Orthopteron shown 
in Fig. 16 are even more like those of the primitive Thysanopteron 
shown in Fig. 14. These similarities may be taken to indicate 
that the Orthoptera, Psocids and Thysanoptera were all des- 
cended from Protorthopt era-like precursors, and inherited much 
the same tendencies from this common ancestry, although these 
tendencies (or the genes, determinants, or what not, which they 
express) were slightly modified by different factors in the differ- 
ent lines of development derived from this common source 
II the Hemiptera-Homoptera were also descended from ancestors 
similar to the Protorthoptera in many respects, this might also 
account lor certain similarities between the Hemiptera-Homop- 
tera and certain Orthoptera, which are too evident to be entirely 
passed over. 
