Vol. XXVli] ENTOMOLOGICAL NEWS. 245 



measure account for the marked difference in the lines of 

 descent here given, and those depicted in Handlirsch's "Fos- 

 sllcn Insekten." 



It is an almost hopeless task to attempt to determine the 

 lines of descent in the different groups of insects, unless one 

 is able to compare together the most primitive representatives 

 of the groups in question, or to make a study of the annectent 

 forms combining in themselves characters common to several 

 groups. On this account, I am deeply indebted to Mr. A. X. 

 Caudell, Mr. C. C. Gowdey, Maj. A. D. Imms, Dr. K. Jordan, 

 and Dr. E. M. Walker for the use of valuable specimens such 

 as Grylloblatta, Timcma, Ari.venia, Labidiirodes, Embia, etc., 

 which have been of the greatest service in furnishing clues to 

 the relationships of the lower insects, and without which the 

 present work could not have been carried on with any degree 

 of certainty or satisfaction. The clues furnished by these 

 primitive or annectent insects have been further carried out 

 and verified by a comparative study of the principal struc- 

 tural features in the different groups of lower insects ; but 

 the detailed discussion of these structures may be more profit- 

 ably taken up in a series of articles, in which they can be more 

 fully treated than in the present paper which is therefore 

 offered as a brief resume of the results obtained from the 

 more extended study of the insects in question. Furthermore, 

 the present discussion is largely limited to the consideration 

 of the lower groups of winged insects, since the rather com- 

 plicated interrelations of the lower insects must be clearly un- 

 derstood, before one can proceed to the study of the higher 

 forms. 



The accompanying diagram is offered merely as an expedient 

 to aid in visualizing the points brought out in the following 

 discussion, rather than as an attempt to portray the actual 

 relations of the various groups, since it is practically impos- 

 sible to depict correctly the true relative positions of the 

 different lines of descent, in a diagram drawn in one plane. 

 It requires a figure of three dimensions to portray the fact 

 that several groups approach each other from different angles, 

 and if an attempt were made to represent this in a diagram 



