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VII. Some Points in the Anatomy of the Larva of Tipula maxima. A Contribution 

 to our Knowledge of the Respiration and Circulation in Insects. By James Meikle 

 Bkown, B.Sc, F.L.S. 



(Plates 24-27.) 

 Read 5th May, 1910. 



1HE respiration of Insects lias always presented features of difficulty. In land forms, 

 with spiracles arranged in series along the sides of the body, a closing apparatus is 

 present which seems to aid in forcing the renewed air into the minute tubules of the 

 tracheal system. The air is probably renewed largely by diffusion. In many aquatic 

 forms, however, there are no open spiracles, but tracheal gills occur, through the walls 

 of which air must diffuse into the ramifying air-tubes contained within the gills. An 

 intermediate type is met with in the so-called " metapneustic " forms, where the air- 

 tubes are open at the posterior end only through one pair of spiracles. One must 

 suppose that greater difficulty will be experienced in these types in renewing the air 

 contained in the smaller branches, and some additional structures might be supposed to 

 be necessary. Further, no closing apparatus (valves) seems to occur within these 

 spiracles, and no regular contractions ("breathing movements") of the body can be 

 distinguished. 



It was to study a form of this kind that the examination of the larva of Tipula was 

 taken up, in the hope that it might throw some light on the question. 



Further, in three such larvae as those of T. oleracea, T. maxima, and T. eluta we 

 have a progressive series, for the first is terrestrial, the last aquatic, and the second 

 amphibious, and it was hoped that some progressive modification from land to w r ater 

 mode of life might be discovered. This has proved to be the case to some degree. 



The most detailed study was made with the larva of T. maxima. Specimens of different 

 age were kept alive and observed. Some were traced through their transformations. 

 The structures were worked out, partly by dissections and partly by serial sections. 

 Material was fixed in different ways, but picro-corrosive, and a mixture of picric acid, 

 corrosive sublimate, acetic acid, formed, and alcohol, used hot, gave the best results. 

 Various stains, including iron-haematoxylin, Delafield's haematoxylin, hsemalum, orange G, 

 fuchsin, and eosin, were tried. Living specimens were injected with carmine to 

 determine, if possible, the function of the pericardial cells. 



My best thanks are due to Prof. Denny, M.Sc, for advice throughout the work, and to 

 Mr. T. J. Evans, B.A., for suggestions and help in staining and preparing sections. 



SECOND SERIES. — ZOOLOGY, VOL. XI. 



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