LABIUM OF ANAX JUNIUS. 2Q5 



1. But one pair of muscles breaks down (the abductors of the 

 lateral lobes) during transformation. The remainder are reduced 

 in size and changed in their attachments only in so far as the new 

 functional conditions necessitate. 



2. Changes in the function of certain pairs is clear, as in the 

 secondary flexors which take on the duty of abduction in the imago. 



3. Two pairs of muscles are here described for the first time : 

 the secondary extensor, and the secondary flexor muscles. New 

 details regarding the mechanism of extension and flexion are also 

 described. 



BIBLIOGRAPHY. 



1. Amans, P. 



'81 Recherches Anatomiques et Physiologiques sur la Larve de 1'Aeshna 

 grandis. Revue des Sciences Naturelles (3), I., pp. 63 to 74, pi. II. 

 Montpelier. 



2. Butler, Hortense. 



"04 The Labium of the Odonata. Trans. Am. Ent. Soc., XXX., pp. in to 

 134, PI. II.-VII. Philadelphia. 



3. Calvert, Philip P. 



'93 Catalog of the Odonata of the Vicinity of Philadelphia, with an Introduction 

 to the Study of this Group of Insects. Trans. Am. Ent. Soc., XX., 

 pp. 1520 to 272, PL II. and III. Philadelphia. 



4. Tillyard, R. J. 



'17 The Biology of Dragonflies. Cambridge University Press. 



DESCRIPTION OF FIGURES. 



All figures are of the labia of Anax junius. The drawings were made through 

 the camera lucida or to measurement by the author. Dotted lines indicate the 

 forms of parts which underlie others and which could usually not be seen without 

 further dissection or the clearing of the specimen. The magnifications are expressed 

 in diameters. 



adl adductor muscle of the lateral lobe. 



abl abductor muscle of the lateral lobe. 



be buccal cavity, mouth parts removed. 



ca carina. 



exp primary extensor muscle. 



eh end hook. 



exs secondary or accessory extensor muscle. 



fxp primary flexor muscle. 



fxs secondary or accessory flexor muscle. 



hb hind border of the head. 



hy hypo-pharynx. 



hd head, sectioned. 



kr chitinous T-shaped rod. 



