Vol. XXVli] ENTOMOLOGICAL NEWS. 257 



two distinct groups of insects, and such annectent forms as 

 the nymphs of Pcltopcrla serve to bring the Plecopteron line 

 of descent very close to that of the Lepismids ; so that I am in- 

 clined to believe that all of these lines of descent of the Or- 

 thopteroid insects ultimately approach very close to that of 

 the Lepisma-like forms, as is shown in the diagram. It should 

 be borne in mind, however, that since no group of living in- 

 sects is descended from any other group of living insects, 

 close resemblances are largely an expression of close parallel- 

 ism in the lines of descent. 



Before leaving the discussion of the lower winged insects, 

 it is necessary to briefly touch upon the relationship of the Li- 

 bellulid, Ephemerid and Neuropteron groups to each other and 

 to the Orthopteroid groups of insects, since the Libellulids, 

 and Ephemerids in particular, are very primitive, although 

 somewhat aberrant types of insects. By the term "Orthopter- 

 oid" is meant all of those Pterygotan forms whose lines of de- 

 velopment approach that of the Blattids or Perlids (e. g. the 

 Perlids, Phasmids, Phylliids, Locustids, Tettigonids, Gryllids, 

 Grylloblattids, Forficulids, Embiids, Termites. Mantids and 

 Blattids). 



The Libellulid group or Pansy go ptcra (i. e. Zygoptera and 

 Anisoptera) is apparently related to both the Ephemerids and 

 the Neuroptera (i. e. the line designated as the Neuroptera- 

 delphia) and also approaches closely to the Perlid-Embiid line 

 of descent, as is indicated in the diagram. The Libellulids 

 may perhaps be regarded as occupying a position intermediate 

 between the Neuropteroid insects, such as the Ascalaphidae, 

 etc., and the Perlid-Embiid group, but possibly ultimately ap- 

 proach the Ephemerid line of descent. 



The Ephemerid line of descent is a rather puzzling one to 

 trace. It approaches the Neuropteron group, and also ap- 

 proaches the Libellulid ("Odonatan") line of descent, but 

 ultimately appears to draw near to the Perlid line, as shown 

 in the diagram, although it does not parallel this line as closely 

 as one might be led to expect from the rather close relation- 

 ship between the Ephemerids and the Neuropteron group. 

 The Ephemerids are in certain respects among the most 



