fiV R. .1. TILLYARD. 



411 



ht 



DT 



epithelium, which })n)ject into the rectiuii, i-i.siiig ami falling with 

 a somewhat luiclulating motion. These folds are shown in Text- 

 fig. 5. I could not detect any sign of a mid- 

 dorsal fold, such as can he seen in older 

 larvae No trachea? can he seen in these 

 folds. 



AVhen the larva is half-an-hour old, or a 

 little older, the regular movements of the 

 rectum cease. Thereafter, the rectum is, for 

 the most part, closed. But, every now and 

 again, it is opened for a short period, during 

 which the movements are again renewed. 

 Larva- were watched from time to time until 

 they were one or two days old, always with 

 this same result. We must conclude, there- 

 fore, that intermittent rectal respiration is 

 carried on by young Zygopterid larva? during 

 the Hrst day or two of their existence, but that it is only regular 

 and viyoroKs/or a, short period directly after hatchliuj. 



Calvertt has given an excellent summary of the present state 

 of our knowledge of rectal respiration in Zygopterid larvje. His 

 own experiments on the larvae of Calopteryx macidata {l.c.,pA'SS) 

 are of more value than all the isolated observations of previous 

 authors. By the use of carmine-particles, he proved that this 

 larva expels water regularly from its anal aperture, '-Vo or more 

 times per minute. He also made similar observations on larv;e 

 of Het(erina{l.c., p. 440), and Anjia {I.e., p.442), in both of which 

 he proved that rhythmic pulsations of the rectum were carried 



Text-fiff.5.* 



* Last four abdominal segments of newly-hatched larva (jf Avxtrolestes 

 I tela iSelys; ( x 100); dorsal view, U> show the paired, latero- ventral, rectal 

 tolds(*;/"). DT, dorsal tracheal trunk; hf, heart (dotted outline); Icj, 

 lateral caudal gill, witii single main trachea; mr<j, median, caudal gill, 

 with two main trache;e; /;/", rectal folds; 7-10, abdominal segments. 



t " Studies on Costa Rican Odonata. vii. Internal Organs of Larva, and 

 the Respiration and Rectal Traeheation of Zygopterous Larva; in General."' 

 Ent. News, Philadelphia, xxvi., pp. 435-447, 1915. 



