112 University of California Puhlications. [Entomology 



of the simpler type, thus indicating that the heteropterous 

 wing was ver}^ early developed. There is even ground for 

 supposing that the Homoptera were at one time heteropterous, 

 though of course this is improbable. 



Most of the remains supposed to be of this group are very 

 unsatisfactor}'^ for the study of venation, and it is more than 

 possil)le that some of the fossils supposed to be homopterous 

 do not, in fact, belong here at all. It will be quite impossible 

 to give a satisfactory diagram illustrating the venation of this 

 group. 



ORTHOPTEROIDEA. 



The oldest known fossil insect shows evident relationship 

 with the Blattidse. Numerous similar forms, and others sug- 

 gesting the Phasmidfe and Acrididct, constitute the fossil group 

 usually placed in the Orthoptera, but considered by Scudder 

 as not sufficiently differentiated from other Paleozoic forms to 

 warrant the assignment. 



The Pala'oblattidie, which have been considered by some 

 authors as representing the most primitive insects, have the 

 most characteristic and distinct venation of any of the Paleo- 

 zoic insects, the other Orthopteroidea being more like the 

 other insects of that era. If the position is well taken that the 

 Paheoblattida? are the most ancient of known insects, then the 

 first differentiation was that which separated off the other 

 Orthoptera, from whose ancestral form the other groups arose 

 later. A more reasona))le hypothesis, however, is, that the 

 Paheol)lattidfe represent an early specialization, the extreme 

 member in a series that specialize in such a way as to pro- 

 vide for the protection of the hind wing by the front wing, the 

 cause being the same as that by which the Hemipteroidea were 

 specialized. The difference between these groups concerns 

 chiefly the mouth parts, but there are differences in venation 

 resulting from the adoption of a somewhat different method 

 of coming to rest. 



In the Pala;oblattida? the thickening of the wing was brought 

 about by the enlargement and strengthening of the longitu- 

 dinal veins, causing them to lie quite strictly parallel, and 

 resulting in a very favorable object for preservation in the 

 rocks. It thus comes about that there is a large series of these 

 fossils known, and their venation is very easily made out. 



