No. 025] TUK KVOIJ'TIOX OF JinilEOPODS 173 



pleteness of the fossil record, rather than to the absence 

 of Dermapteron forms antedating the Coleoptera. 



The Isoptera, blattids and mantids seem to have 

 originated from a stock similar to the members of the 

 Plecopteron group mentioned above (Crampton, 1917a) 

 and they apparently branched off at a very early date to 

 follow their own developmental road for a short distance 

 before each of tlu^ throe se])arated to follow its own path 

 of deve]oj)ni(Mit. Tlic lso))tera are anatomically inter- 

 mediate between the iiKMiibers of the Plecopteron group, 

 and the rest of the l)hittid uroiip (with whicli the Isoptera 

 seem to have somewhat sti-oiigor affinities than with the 

 members of the Plecoi)teron group, although tiiey are 

 related to the embiids and Dermaptera (juite closely). 

 This might be taken to indicate that the Isoptera are 

 more primitive than the blattids, as is borne out by cer- 

 tain of their anatomical features; but on the whole, the 

 blattids seem to be somewhat more lowly organized and, 

 according to HandlirRch, the Tsoi)tera are paleonto- 

 logicallv much voiiiiger than the ))lattids. It is quite 

 pro})abie that the Zorav>tera described ])y Silvestri, 1913, 

 are an offshoot of the i^.M.ieioti <t.>ek. 



The orthopteroid iiiM-rt^. \ llnhiani.U and phasmids 

 were descended from aiice-tni'^ very -iiuiiar to Gryllo- 

 hlaffa reeentlv dexM'iixMl l.y Walker. 1914. and such 

 plia^niids as Timmhi are aUo x ,m-> near tlie ha^. of the 



chara'eters tVoni tlie i)lee.>]»ter<)i(l nde ,>i their anc'-try, 

 and they also share many featinvs in vomuum with the 

 blattoid grou]) mentioned above (see (^rampton. I!»17f7). 

 Their line of descent is apparently ultimately traceable 

 to a plecopt(M-oi(l ance-try (a^ i^ pr()1)al)ly aNo the case 

 with the blattoid forms), but their line of development 

 branched off very near that of the blattoid group, and 

 they continued to ])arallel the ].atli of (leveloj.ment of the 

 latter li-roup for a eoiisidrrable .li-tan.-.. hcfore divero-ing 

 alonu- thei,. o^^u hran.-h m' .p.eia li/athm. Ti'e urxUo- 

 blatti.N M'eni to h- -..meuhat <-loM"r to the ai;.M-Pn- of 

 the grvllids aiMl om^i.K.-' uhile tlie phaHnids nia> be 



