102 PROCEEDINGS OF THE ACADEMY OF [March, 



of gases are the longitudinal folds of spongy or reticulate tissue. 

 In this connection it may, or may not, be worth noting that 

 Calvert (1911 h, p. 453 and Plate XVII), in dissecting Mecistogaster 

 larva No. 1, found, "when the viscus was first opened the three 

 non-cellular bands [folds of spongy tissue just referred to] had the 

 shiny, silvery appearance which suggests enclosed air." But, 

 since these areas either lack entirely or have a very scanty tracheal 

 supply, the oxygen would have to be taken up and carried by the 

 blood.^ 



We are not able to correlate any peculiarity of the tracheation 

 of the larva of Mecistogaster modestus with its habit of living in the 

 water between the leaf-bases of epiphytic bromeliads (Calvert, 

 1911 a). 



In the study of these slides and in the preparation of the manu- 

 script I am indebted to Dr. Calvert for suggestions, directions, and 

 corrections. 



Literature Cited. 



(For a more complete bibliography on the respiratory organs and the 

 physiology of respiration of Zygopterous Odonate larvae see Calvert, Ent. News, 

 Vol. XXVI, p. 444). 



BoDiNE, J. H. — 1918. Papers on the Rectal Tracheation and Rectal 

 Respiration of the Larvae of Odonata Zygoptera. IV. Experimental Results 

 in Ischnura and Enallagma. Proceedings Academy of Natural Sciences of 

 Philadelphia, LXX, pp. 103-113. 



BoRDAS, L. — 1898. Appareil Digestif des Orthopteres. Ann. des Sc. Nat., 

 Zoo. VIII, 5. 



Calvert, P. P. — ^1911, a. The Habits of the Plant-dwelling Larva of 

 Mecistogaster modestus. Ent. News, Vol. XXII, pp. 402-411. 



— 1911, b. Structure and Transformation of the Larva of Mecistogaster 

 modestus. Ent. News, Vol. XXII, pp. 449-460. 



— 1915. Internal Organs of Thaumatoneura Larva and the Respiration 

 and Rectal Tracheation of Zygopterous Larvae in General. Ent. News, Vol. 

 XXVI, pp. 385-395, Nov.; pp. 435-447, Dec. 



CuLLEN, A. M. — 1918. Papers on the Rectal Tracheation and Rectal 

 Respiration of the Larvae of Odonata Zygoptera. I. Rectal Tracheation of 

 Argia putrida larva. Proc. Acad. Nat. Sci., Phila., LXX, pp. 7.5-81. 



Faussek, V. — 1887. Histologie des Darmkanals der Insekten. Zeit. f. 

 wissench. Zool., 45. 



Jamieson, J. P. — 1918. Papers on the Rectal Tracheation and Rectal Res- 

 piration of the Larvae of Odonata Zygoptera. II. The Tracheal Supply of the 

 Rectum of the larva of Argia talamanca from Juan Vinas, Costa Rica. Proc. 

 Acad. Nat. Sci., Phila., LXX, pp. 81-85. 



MiNOT, C. S. — 1880. Histology of the Locust (Caloptenus) and the 

 Cricket (Anabrus). Second Rept. U. S. Ent. Comm., pp. 183-222. 



2 Tillyard suggests (1917, p. 116) that in Zygopterid larvae the rectal pads 

 (glands or folds) act as blood-gills, liberating carbonic acid gas from the blood 

 into the rectal water supply, by diffusion, and receiving air in exchange. This 

 hardly seems likely. The blood is separated from the water in the rectum by 

 the basement membrane, the thick (41 to 83 micra) columnar epithehum and 

 the chitinous intima. 



