28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



held far — touch the cylinder only at two points during- each beat, 

 or — when it is held closer- — produce a curve so blurred that not much 

 can be learned from it. On account of this, Marey's kymographic 

 tracing^s do not show very much. 



The third method is v. Lendenfeld's (1903) photographic method, 

 by means of which series of instantaneous views of flying insects 

 can be obtained (pi. 19, fig. 53). 



The above statements show that the problem of applying the 

 kymographic method to the study of insect flight had not been sat- 

 isfactorily solved. I tried, therefore, to adapt that method better 

 to this end by devising a new kind of flight-kymograph (pi. 14, 

 figs. 35, 36). This consists of a wooden frame 120 cm. long and 

 20 cm. high. In grooves in the upper and lower parts of the 

 frame there slides a thin board, 50 cm. long. This board can be 

 rapidly shot from one end of the frame to the other by means of a 

 steel spring. To this movable board is attached a horizontal groove, 

 semi-circular in cross-section ; the radius of the semi-circle being 

 equal to the average length of a blow-fly's wing. In this groove a 

 strip of glazed, blackened paper is fitted. 



A fly in the normal horizontal position is held fast before the 

 groove with the blackened paper so that the root of the wing lies 

 at a point of the axis of the semi-cylindrical surface formed by it. 

 When the fly attempts flight the tip of the wing touches the black- 

 ened paper. The stop holding the spring is then withdrawn, the 

 board with its groove and blackened paper slides past the fly and 

 the tip of the insect's wing describes a curve on the latter. Curves 

 procured in this way are shown on plates 16, 17 and 18. 



Flight 



If the fly remains at the same place in the air (hovers), as is 

 frequently observed among the Syrphidse, each tip of the wing de- 

 scribes a figure 8. Although this fact was already known to Petti- 

 grew, the general relations and the special peculiarities of this 

 figure 8 have never been studied in detail. The tracings made with 

 my flight kymograph (see above) show several things that had 

 escaped the attention of Marey. In regard to the inclination of 

 the 8 to the horizon, it was found that the long axis of the 8 is 

 directed from above and behind, downward and forward,' and that 



^ The expressions upward, downward, forward, and backward are always 

 used in relation to the body of the fly. 



