272 



Notes on the derivation of winged insects throngh several lines etc. 



is difficult to conceive of any other war of interpretiog this fact than 

 on the assuiTjption that they are the descendents of a common ancestor. 

 It is preferable to regard the Japix-like forms as the common ancestors 

 of both Coleoptera and Dermaptera, rather than to attempt to derive 

 the Coleoptera from the Japyx-like forms throngh the Dermaptera, despite- 

 the fact that the earwigs are in manj respects much more primitively 

 organized than the Coleoptera. 



The Mjriento-Platj'ptera line, leading from the Mjrientomata to 

 the Platyptera (i. e. the Plecoptera and Embioidea) is a much more 

 primitive one, or branched off from the common stock much lower 

 than the Dicelluro-Dermaptera line, and includes forms which are, 

 structurally speaking, among the most primitive of the apterj'gote and 

 pterygote insects. In some respects, the Plecoptera are more closely 

 related to the Mjrientomata (such as Eosentomon) than the Embioidea 

 are, and may possibly represent a stage of development intermediate 

 between the Embioidea and the Myrientomata (i. e. the lines of deve- 

 lopment would be expressed as the Myriento Plecoptera and the Pleco- 

 ptero-Embioidea lines). Provisionally, however, I prefer to consider 

 the Myrientomata as the common ancestors of both Plecoptera and 

 Embioidea, so that it is preferable to express the developmental series- 

 as the Myriento-Plecoptera and the Mjriento-Embioidea lines of descent^ 



Torning for a moment to the consideration of the higher forms^ 

 such as the Diptera, Mecoptera, Trichoptera, Lepidoptera and Hemi- 

 ptera, a comparative study of the anatomy of these forms suggests 

 a Community of descent from ancestors whose nearest living represen- 

 tatives are to be found in the heterogeneous group Neuroptera.* From 

 the ancestors of the Neuroptera, there have been given off several lines- 

 of descent. One of these is the Neuroptero-Trichoptera line, which either 

 gaye rise to a Trichoptero-Lepidoptera line, or is closely related to 

 a Neuroptero-Lepidoptera line. Another line near these is the Xeuro- 

 ptero-Mecoptera line leading to the Panorpidae, and quite near those 

 mentioned above, is the Neuroptero- Diptera line. To these may be 

 added the Neuroptero-Homoptera line, which is doubtless a composite 

 one, but for the sake of brevity, it may be signated simply as the 

 Xeuroptero-Homoptera line, without attempting to resolve it into its 

 component parts. 



Thus far, it has been comparatively „smooth sailing", but 

 when we attempt to trace the Neuroptera to some one of the more 

 primitive types, we at once encounter considerable difficulty. One of 

 the most promising lines to suggest itself, is the Platyptero-Neuroptera 

 line leading from the Plecopteron branch of the Platyptera, to the 

 Neuroptera (it might be more exact to refer to this line as the Pleco- 

 ptero-Neuroptera line, since it leads from the Plecopteron branch, in^ 

 stead of froui the Platyptera as a whole). There may have been 

 a Platyptero-Mantieformia line closely paralleling the latter, and leading 

 trom the Embioidean branch of the Platyptera to the Mantieformia 



*) The Coniopterygoidea, Sialoidea, Hemeroboidea, Nemopteroidea, Mantis- 

 poidea, Raphidoidea, Myrmeleonidea and Ascalaphoidea form a heterogeneous 

 coUection which should be split up into other groups. The Ascalaphoidea, for 

 example, should be placed in another order, the Arcyptera (or net-winged forms)^ 

 and the Myrmeleonidea should perhaps be included with them. 



