THE CANADIAN ENTOMOLOGIST. 159 



pulley made twelve turns for each one made by the lower, and could be caused 

 to rotate twenty-four times in a second. The insects were killed by ether 

 vapor immediately before each experiment; and the wings could be fastened, 

 by a simple coutrivance, to the front prolongation of the axis of the upper 

 pulley. 



A wing, in its folded state, was fixed on the instrument in such a manner 

 that its plane made, with the plane of rotation, an angle of 45°, as in the 

 living animal. On turning the pulleys, it struck the air obliquely by its upper 

 surface and front margin ; but the small diameter of the apparently continuous 

 revolving disc (as indicated by a graduated scale ) proved tbat the wing was 

 still folded, and that centrifugal force had not affected it. When rotation was 

 produced in an opposite direction, so tbat the wing struck the air both by its 

 posterior membraneous margin and interior surface, the increasing diameter of 

 the disc gave proof of the expansion of the wing, which, indeed, continued 

 to be much extended when motion was arrested. Yv 7 hen the plane of awing 

 was perpendicular to the plane of rotation, and the revolution of the wheel 

 was such that the wing struck the air by its dorsal or upper surface, no exten- 

 ion ensued ; when it struck by its lower surface, only partial extension followed , 

 Now the oblique, not the perpendicular plane, is that chosen by nature, and is 

 as has been seen, much more favourable for flight. 



On fixing an open wing on the axis so as to make an angle with the blane 

 of rotation, and turning in one direction, the wing remained open; on reversing 

 the direction {i.e. acting on the upper surface) it became partially closed. 



EXCHANGES, &o. 



Lepidoptera. — Canadian Lepidoptera desired in exchange for British. — 

 E. H. Collins, Daily News Oifice, Kingston, Out. 



Pup^e and Ova of Lepidoptera. — I am desirous to obtain, if possible, 

 lice Pupae and Ova of certain Canadian and other North American Lepidop- 

 tera. "Would purchase, or give in exchange English or other European 

 species. — Chas. Geo. Rotheram-Websdale, 78 High-street, Barnstaple, 

 England. 



Collecting Tour in Western Texas and New Mexico. — At the 

 request of several geutlemen in this country and Europe, I intend to make 

 an extensive eight or nine months Entomological collecting tour in Western 

 Texas and Southern New Mexico, if sufficient means can be raised. I 

 therefore invite every Entomologist, who wishes to enrich his collection with 

 valuable and unknown species, to assist me in the undertaking. To give 



