1919.J , 87 



Ingram and Mactie. t'orliaps alM> the muscles producing the detiection 

 of the anal segment ma\' be attached to the !«\vo]len end of the axial rod, 

 l)ut this 1 have not been able to observe. 



7'. richlartUi has another* remarkable adaptation, apart from those 

 found in the air-tuhe, which has not been previously ohserved, though it 

 may he ex])ected to occur in tlie other species of the group. This is the 

 presence in the tliorax of a pair of large air-sacs, formed by dilatations 

 of the small tracheal branches which arise from the main trunks in the 

 lirst abdominal segment and project forwards into the thorax. No trace 

 of any such dilatations can be seen in any other British mosquito larva, 

 and they are not indicated in the published figures of any American 

 species. They can only he compared with the thoracic air-sacs of 

 Chaoborus (^Corethra) and Jioc/<Zo«^a;, though it is unlikely that they 

 are the same either in origin or function. I think there can be little 

 doubt that the air-sacs of Taenlorhynchus act as storehouses for the 

 oxygen which is obtained with so much difficulty; perhaps they may be 

 necessary for hibernation, since there can only be a very slight gaseous 

 circulation in the grass roots during the winter. 



The pupa of Taeniorliynclius, like the larva, is adapted [to a sub- 

 aqueous existence, the tips of the breathing-trumpets being drawn out 

 into sharply pointed processes which are inserted into the grass roots. 

 Although 1 have not found a living pupa, and all my larvae died before 

 pupating, a balsam mount of one specimen shows the pupal breathing- 

 tube.s very clearly. The terminal portion, which is presumably inserted 

 into the root, has a beautiful structure, being finely ridged or barbed, 

 somewhat like a feather, the tip corresponding to the feather's base. 



The mode of emergence of the adult T. ijerturhaas has not been 

 made known, and it will therefore be of interest to record that several 

 spiecimens of T. rickiardii hatched out in a pail which 1 had brought 

 home with pond- water ami sods of the grass. The empty pupal skins Avere 

 found floating on the surface of the water, and the pvipae must therefore 

 have risen to the surface for the emergence of the adult. An examina- 

 tion of these skins showed that in every case the terminal portions of the 

 bre'athing-tubes were missing, hence it must be inferred that they had 

 been left behind in the roots. Most likely their barbed structure, while 

 facilitating their insertion, would jjrevent their being withdrawn. There 

 seems to be a line of weakness at the base of the barbed portion which 

 might render its detachment easy. 



In conclusion, it may be briefly mentioned that several other 

 Dipterous larvae were found in the same conditions as T. richiardii, 



