116 Psyche [October 



NOTES ON THE LINES OF DESCENT OF LOWER 

 WINGED INSECTS. 



By G. C. Crampton, Ph.D., 

 Massachusetts Agricultural College, Amherst, Mass. 



In the February issue of the Entomological News for 1919 (Vol. 

 XXX, p. 42) the lines of descent of the Orthoptera and their im- 

 mediate relatives, were discussed from the standpoint of the com- 

 parative morphology of recent forms; but no attempt was made 

 at that time to bring the results into harmony with the conclusions 

 of Handlirsch, 1909 (Die Fossilen Insekten), who has attacked the 

 problem from the standpoint of palaeontology. I would, there- 

 fore, offer the following brief suggestions as to the location of the 

 lines of descent of certain of the fossil forms described by Hand- 

 lirsch, in the general scheme of the interrelationships of living in- 

 sects. It should be borne in mind, however, that since the earlier 

 fossil forms are known almost exclusively from their wing- venation, 

 the position they are assigned in the general scheme is largely con- 

 jectural, and must remain so until more of their anatomical details 

 than the few incomplete fragments thus far brought to light are 

 known — for the wing- venation alone (or any other one set of struc- 

 tures) is entirely insufficient evidence upon which to base one's 

 conclusions as to the interrelationships of insects. A good illustra- 

 tion of this point is furnished by the fossil insect Eugereon, in 

 which the wings are very conservative {i. e., but slightly modified) 

 while the head has proceeded far along the road to specialization — 

 so much so, in fact, that it would be practically impossible to place 

 Eugereon correctly in the general scheme, if it were known only 

 through the venation of its wings. In the recently discovered 

 winged Zoraptera (Proc. Ent. Soc. Washington, Vol. 22, p. 84, and 

 p. 98), on the other hand, the wings are quite highly specialized, 

 while the body structures are quite conservative, and if the de- 

 tached wings were the only structures known, it is very doubtful 

 if we would be able to place these insects in their correct position 

 next to the line of development of the Isoptera. 



As was pointed out in the August, 1919, issue of the Transactions 

 of the Entomological Society of London (p. 93), the Ephemerida, 

 Odonata, and certain Palaeodictyoptera form a group characterized 

 by their inability to fold their wings flat along the top of the ab- 



