AMERICAN NEUROPTEKA. Ill 



THE L.ABIUM OF THK ODOXATA. 



BY HORTENSE BUTLER. 



In the selection of this subject for investigation I was influenced 

 primarily by the lack of knowledge in regard to two important 

 aspects of the study of this remarkable appendage. In the first 

 place, up to the present time, no attention whatever has been paid 

 to the mechanism of the labium, and in the second place while 

 some attention has been devoted to the homologies of its parts, the 

 results appear to me incomplete and their supporting evidence 

 insuflicient. 



Aside from the discussion by Gerstaecker, of which a detailed ac- 

 count will be given in the proper place, we have only very few para- 

 graphs embodied in papers on other subjects, by Rambur, Hagen, 

 Brandt, Calvert and Heynions. The object of this paper is to pre- 

 sent such new information as has been obtained and to supplement 

 and in some cases correct the old. 



The work has been carried on entirely in the biological laboratory 

 of Lake Forest College and under the supervision of Prof. J. G. 

 Need ham. 



The adult material used was obtained entirely from his collection, 

 with the exception of some specimens loaned by the U. S. National 

 Museum, the Museum of Comparative Zoology, and the Imperial 

 Museum of Berlin, which were at that time in his possession. The 

 series of mounted adult labia studied was prepared by me from 

 specimens obtained from this source. With regard to the ontoge 

 netic material, the eggs of Anax Junius were obtained when laid by 

 collecting stems in which the females were observed ovipositing, and 

 developed in confinement. The embryonic stages studied were taken 

 from eggs respectively seventeen and twenty days old. The embry- 

 onic stage of Lestes uncata was obtained from some aestivating eggs 

 collected by Prof. Needham, and the time which had elapsed since 

 they were laid was uncertain. 



The majority of the drawings were made by me directly from the 

 specimens. A few, however, were made from photographic plates 

 and some from unpublished drawings by Prof. Needham. 



I. The Mechanism of the Labium. 

 Every one who has devoted any attention whatsoever to the study 

 of the Odonata has been impressed by the enormously developed 



TRANS. AM. ENT. SOC. XXX. APRIL. 1904. 



