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 

 coxse 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 Protorthoptera-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 

 If the Hemiptera-Homoptera were also descended from ancestors 

 similar to the Protorthoptera in many respects, this might also 

 account for certain similarities between the Hemiptera-Homop- 

 tera and certain Orthoptera, which are too evident to be entirely 

 passed over. 



