386 ENTOMOLOGICAL NEWS [Nov., '15 



caudal gill of Bayadera indica and ours (Ent. News, xxvi, 

 pi. xi, f . 9) of a median caudal gill of Thaumatoneura is very 

 close. This two-jointed condition is of interest since these 

 gills are homologous to the many- jointed middle tail filament 

 and cerci of Lepisma and of Ephemerid larvae, while the 

 lateral gills are homologous to the several- to many- jointed 

 cerci of Orthoptera and of larval Perlidae (Heymons 1896, 

 1904). Heymons termed the median unpaired "gill" the ap- 

 pendix dorsalis and the other two the appendices laterales, the 

 three collectively appendices caiidales, applying these terms 

 both to Zygopterous and Anisopterous larvae. 



The three caudal appendages of Thaumatoneura larvae, al- 

 though supplied with tracheae whose derivation is homologous 

 with that of the tracheae of the lamellate caudal gills of most 

 Agrionine larvae, present so little surface for respiration that 

 I expected dissection to reveal some rectal tracheal gills com- 

 parable with those of the larvae of the Anisoptera. This ex- 

 pectation has been partly fulfilled but, as will be seen from 

 the present paper, the rectal folds in Thaumatoneura larva are 

 less numerous and each of the three folds less sub-divided and 

 much less tracheated than is the case in Anisopterous larvae. 

 No observations or experiments bearing directly on the meth- 

 ods of respiration were made on the living larvae of Thaumato- 

 neura. We know that in their native waterfalls they are fre- 

 quently found on rock-faces where they are kept moist, but 

 are not submerged, by the falling water. Their movements, 

 both at large and in our rearing glasses, were never rapid. 



Internal Organs of Thaumatoneura Larva.* 

 Alinnentary canal. The pharynx is separated from the oesophagus 

 by a distinct constriction lying a little caudad to the level of the brain, 

 but cephalad to the level of the hind margin of the head ; the oesopha- 

 gus is defined posteriorly by a constriction in the prothorax separating 

 it from the crop (larva no. 6). The external dorsal surface of the oe- 



*Owing to the destruction referred to under the heading "Descrip- 

 tion of the Larvae," Ent. News, xxvi, p. 300, no larvae specially fixed 

 for histological study have been available, and it has been necessary to 

 rely exclusively on larvae nos. 1-9 (/. c), which were placed in alcohol 

 as soon as their deaths were discovered. 



