586 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. YI. 



tionsliip of Cossus and Sepialus, witliin the Bomhyces. We have sur- 

 Yiving in this group a number of tyi3es now comparatively isolated; in 

 arranging them we must be governed by general considerations of this 

 kind. The relationship is net-like, and the survival is unequal. The 

 iSTotodontiaus may be held to be nearer the Noctuidce, but I should not 

 arrange them last on this account; if, by position, we indicate a higher 

 or lower structure, we are bound to finish tho, Bomhyces with the Sepiali, 

 with naked larvae and short antennse in the moth. jS'or can I, on account 

 of the hairy larvge, place any of the Apatela-like genera of the Noctuidce 

 among the Bomhyces. I have explained the characters which have 

 influenced my arrangement of the genera of Noctuidce. There is a 

 general tendency in the increasing breadth of wing and common color- 

 ing of both wings towards the Geometrid type. To a certain extent the 

 sequence is broken by the Deltoids. Yet the higher genera of this 

 group are not separable by structure from the lower forms of the 

 Fasciatcc. It needs only the comparison of Somopyralis and Pseudaglossa 

 to show this. On the other hand, the limit between the lower Deltoids 

 and the Pyralidce is diflicult to define ; certainly, I have been puzzled 

 to locate such a genus as Dercetis. The neuration must guide us; yet 

 how uncertain this character often is, has already been felt by observers. 

 The result of my own studies has been to insist on the present sequence 

 of the families, interpolating the Geometridce between the Noctuidce and 

 Pyralidce. As to the genera, I would keep the Apateloid genera in the 

 Noctuidce; from which family I think it also unadvisable to separate 

 the Cymatophorina of Herrich-Schaeffer. In studying a species with 

 the view of locating it in any family, we must be guided bj^the relative 

 form and, as shown by Dr. Packard, the/acies, in addition to the balance 

 of single structural features. Such consist in the structure of the eyes, 

 antennffi, mouth parts, neuration, and genitalia; the presence of ocelli, 

 the character of the vestiture, the ijattern of marking and color must 

 be ascertained. After all this, a certain tact, Avhich is the result of 

 experience, must be depended upon to successfully place the species. 

 A special discussion of the different forms catalogued by me would be 

 too lengthy and out of place. I would merely endeavor to interest the 

 reader and lead him to investigate the mauy questions which are not 

 finally answered. The time is coming when our classifications will be 

 greatly influenced by a knowledge of extra-limital forms. The student 

 of a group as represented throughout the globe must be relied upon to 

 place correctly the species in a single fauna. For this reason MM. 

 Boisduval and Guen^e have been, and now Mr. Butler and Professors 

 Speyer and Zeller are, in the best position to give a weighty opinion. 

 The SpMngidce of the world in the cabinet of the British Museum afford 

 their describer many facts which influence the arrangement of the North 

 American species. It was not without a survey of this and other large 

 collections that I adopted the present arrangement of our forms. I was 

 glad to find that our earlier Synonymical Catalogue offered main points 



