12 



PSYCHE. 



[January 1S91. 



ranged in converging bars according to 

 their supposed relations during geologic 

 times. This last is purely theoretical, 

 since the present state of our knowledge 

 of fossil insects is too fragmentary and 

 unsatisfactory to afford sufficient evi- 

 dences for the demonstration of such a 

 classification. 



Diagram II [pi. I] represents the op- 

 posite or farther side of Diagram I, 

 the plate having been turned around 

 so that the orders X-XVI can be more 

 clearly seen both above and below the 

 earth's surface. Diagram III is a view 

 from above the circular plate giving in 



Diagram III. 



horizontal section the position of the 

 orders. In Diagrams I, II, A repre- 

 sents the wingless, primitive, or Thy- 

 sanuran stock. The stems B, B'\ 

 B'" * , Diagram I; B\ B 1V , Diagram 

 II, represent the winged stocks which 

 sprang from A. These may have been 

 composed, so far as the facts now known 

 are concerned, of a number of separate 

 or branching lines leading up to the 

 various orders as termini of more or 

 less distinct stocks. f 



The line B' in Diagram II indicates 

 the winged stock from which the true 

 Neuroptera sprang, and so far as we 

 know, this may have been the same 

 common stock as that from 

 which the Ephemeroptera and 

 Odonata also arose (Diagram I, 

 B) . In spite of the introduction 

 of the quiescent pupal stage in 

 the Neuroptera, their obvious 

 resemblances to the Odonata, 

 and the fact that they still retain 

 the Thysanuroid form of larva 

 should not be overlooked. Dia- 

 gram I recognizes these simi- 

 larities, and presents the least 

 modified and most ancient 

 branches of the genealogical 

 tree of the Insecta as near to- 

 gether as practicable. The 

 placing of Thysanura near the 

 centre, by means of a short 



* Bl ' I extends in the diagram to the orders Hemiptera and Thysanoptera instead of to the stem from which 

 these orders sprang. It is placed here because the stem proper is out of sight, being farther down and behind B 

 and B I I. 



t For example, as suggested by Packard in Third Rep. U. S. Ent. Com., p. 2S9, the Dermaptera may have been 

 derived from a form similar to Japyx, a curious Thysanuran genus, and since it has characters allying it bolh to 

 Orthoptera and Coleoptera, it may be the existing descendant of some common forms from which both of these 

 orders originated. The Thysanura stand, according to Comstock, in a similar position with relation to the Hem- 

 iptera. 



