122 Psyche [October 



GRYLLIDAS ELCANIDAE 



GRYLLOTALPIDAE \ / lOCUSTOPSIDAE 



LOCUSTIDAEv \ \ / / TRIDACTYLIDAB 



PHASM0DIDA11..^\^^ \\ // /^ACRIDIDAE 



GRYLLOBUTTIDA^ nS, \1 \ I / / ^CHRSSMODIDAS 



PROTORTHOPTERA ^ -^^'"^ ^ .^PHASMIDA 



Fig. 4. Lines of descent of the Panorthoptera. 



Timema, however, give us a much better idea of the structural 

 details of the lower representatives of the group, since the fossil 

 forms are too poorly preserved for this purpose. Grylloblatta is 

 structurally intermediate between the Zorapteron-Isopteron group 

 and the Dermapteron-Embiid group of insects, while Timema ex- 

 hibits more Plecopteroid characters than Grylloblatta does. In fact 

 Timema exhibits such pronouncedly Plecopteroid features that 

 there can be no doubt that the Plecoptera and their relatives rep- 

 resent the ancestral forms from which such insects as Timema (and 

 hence those insects grouped with it) were derived. Of the other 

 Orthopteroid insects, the Gryllidse and "Locustidse" (Tettigoni- 

 idae) are very like Grylloblatta, while the Acrididse {i.e., true Locus- 

 tidse) and Tridactylidse are nearer the Phasmidse. 



According to Handlirsch, the fossil Chresmodidse are very closely 

 related to the Phasmidte, and are intermediate between the Phas- 

 midffi and the fossil Elcanidse, from which Handlirsch would derive 

 the Tridactylidse. Handlirsch derives the Acrididse from the fossil 

 Locustopsidse, and he considers that the Elcanidse and Locustopsi- 

 dse are somewhat intermediate between the Acrididse and the 

 Locustid-Gryllid group, so that they have been assigned this posi- 

 tion in the diagram shown in Fig. 4 — although the diagram in 

 question is somewhat different from that given by Handlirsch to 

 illustrate the interrelationships of the forms in question, especially 

 with regard to the position assigned to the Phasmidse, which Hand- 



