Dec, 1917.] Crampton : Abdominal Segments and Appendages. 233 



Pandictyoptera, the Mantids are somewhat closer to the Blattids 

 than the Isoptera are, and the Isoptera are much nearer the Blattids 

 than they are to the Mantids. The Psocids, which are placed near 

 the Isoptera by Handlirsch (and are grouped with the Isoptera and 

 Embiids by Enderlein) are in reality extremely closely related to the 

 Neuroptera instead, and have departed but little from the ancestral 

 condition of the Homoptera. The relationships here expressed are 

 based upon a study of structures located in widely different parts 

 of the body, and the agreement in a great number of details precludes 

 the possibility of being deceived by a mere " convergence " or paral- 

 lelism of development due to a similar mode of life, or other causes! 

 It is necessary, however, first to take up each region of the body in a 

 series of comparative studies of the most important structures, giv- 

 ing especial weight to those which vary but little within an order; 

 and until this is done we have no really firm basis for determining 

 the ancestry and interrelationships of the lower orders, for " one 

 man's opinion is as good as another's " in such matters, and it is only 

 by citing the facts of the case, and supporting one's statements by 

 drawings of the parts in question, that one's opinions concerning the 

 relationships of the orders of insects can carry any weight. On this 

 account, it is preferable to defer the summing up of the numerous 

 structural resemblances upon which the relationships here proposed 

 are based, until the series of comparative anatomical studies (of 

 which the present paper, and the one dealing with the lateral head, 

 neck, and prothoracic regions, are a part) is more nearly completed, 

 and the figures of the parts in question are available for reference 

 in the discussion, since it would make too bulky and expensive a paper 

 to attempt to publish all of these figures in a single article. 



Bibliography. 

 1880. Berlese. Ricerche sugli organi genitali degli Ortotteri, in: Atti R. 



Acad. Lincei, XI. 

 1909. Berlese. Gli Insetti. 

 1880. Brehm. Struttura comp. dell' organo riprod. della Blatta e della 



Periplaneta, in: Mem. Soc. Ent. St. Petersburg, 8. 

 1876. Brunner von Wattenwyl. D. morphol. Bedeutung der Segmente 



etc. bei Orthopteren, in : Festschr. Zool. Botan. Gesell. Wien. 



1908. Bruner von Wattenwyl. Die Insektenfamilie der Phasmiden, Leipzig. 



1909. Bordas. Recherches anatomiques, etc. sur les organes appendiculaires 



de I'appareil reprod. femelle des Blattes, in : Ann. Sci. Nat. Zool., 

 9, p. 71- 



