22 ENTOMOLOGY 



Orthoptera probably arose directly from the original thysanuri- 

 form stem. Of Orthoptera, Blattidae are the most primitive, with 

 Mantidae closely allied to them. In a linear arrangement, Gryllidae 

 may follow, though not closely related to Mantidae. Between Gryl- 

 lidae and Tettigoniidae (formerly Locustidae) comes Walker's new family 

 Grylloblattidae, which a few authors prefer to regard as a new order. 

 Tettigoniidae and Locustidae (formerly Acridiidae) belong together. 

 Phasmidae have some affinities with Locustidae, but show the greatest 

 departure from the primitive orthopteran type. 



Dermaptera, represented almost entirely by the family Forficulidae, 

 which some authorities still retain in the order Orthoptera, must have 

 come from the same ancestors as Orthoptera, needless to say. In 

 some respects they are more primitive than Orthoptera; in others, more 

 specialized. Though the order shows some thysanuran characters, 

 the resemblance between a young earwig and the thysanuran Japyx 

 (both having forceps, for example) is on the whole superficial; the mouth 

 parts of the two agreeing only in the broadest way. On the other hand, 

 the resemblances in structure between Dermaptera and Coleoptera 

 are deep-seated. The dermapteran genus Hemimerus has strong 

 affinities with the orthopteran family Blattidae. 



The suborders of Platyptera are by some raised to the rank of 

 orders. They are so closely related, however, that it seems preferable 

 to the writer to express their resemblances by keeping them together, 

 rather than to emphasize their differences by separating them. 



Platyptera, as a whole, are most nearly related to Orthoptera on the 

 one hand and to Plecoptera on the other; Isoptera and Embioptera in 

 particular being strongly orthopteran. Mallophaga, aside from their 

 parasitic characters, agree closely with Corrodentia, especially as 

 regards the structure of the head and mouth parts. The bird lice are 

 essentially degenerate descendants of psocid-like ancestors (Snodgrass). 



Zoraptera, represented by six species of the genus Zorotypus, is 

 held to be a distinct order by some authors. A few years ago, Zoro- 

 typus would have been placed without hesitation among the termites. 

 The species of the genus are essentially termites, with a wing venation 

 suggesting that of psocids. 



Plecoptera, which Packard placed in his order Platyptera, show 

 many primitive characters, including thysanuriform nymphs. 



The more generalized winged insects fall naturally into two 

 groups, which are not sharply separated, however: orthopteroid and 

 plecopteroid. The latter group consists of the aquatic orders Plecop- 



