306 Dr. T. A. Chapman on 



the weight of the wings thus hanging tending to raise 

 them from the level body plane. The suggestion is, that 

 the wings would have been horizontal had the line of the 

 body actually been so. 11.50, wings thrown back. If 

 the surface from which the moth is hanging be gently 

 placed horizontally then the wings fall to within 20°, 

 sometimes little more than 10° from being horizontal also. 

 Pieris rapae. — The wings expand in six minutes, and 

 then hang down quite straight, touching the opposite wing 

 only by the tips. (PI. LXXX, fig. 5 a.) The wings are 

 after another six minutes separated ; they are limp, and 

 hang (as seen from the costal aspect), in somewhat bell- 

 shaped fashion, outwards at the base and quickly curving, 

 so that three-fourths of the wings hang vertically, the 

 hind-wings closely touching the fore ones (b). Then they 

 are closed again. Curiously, like T. quercus, the change 

 from separation to shut and back again takes almost 

 exactly a minute, the period of being separate varying, 

 however, from 30" to 45", generally about 36" to 40" 

 (c, d). In about six minutes the wings are not so limp, 

 but a little straighter, and the hind-wings hang slightly 

 separate from the fore-wings (e). In four or five more 

 minutes the wings seem quite straight, and when separate 

 the hind-wings are apart from the fore- wings (/). At 

 the end of thirty minutes from the first movement of 

 separating the wings, the period of separation is a little 

 prolonged ; the tips of the fore-wings now touch, but the 

 costae are well apart and the hind-wings separate and, 

 if anything, rather divergent, about 3 mm. from costa to 

 costa. The wings hang thus, with faint opening and closing 

 movements producing little effect, for ten to fifteen minutes, 

 without completely closing; they arrive, however, after 

 this interval at having the tips in contact and very gradually 

 in some further ten minutes reach the permanent resting 

 attitude (g, h, i). In separating the wings the movement is 

 quick, almost sudden ; the closing is slow, taking several 

 seconds. In the " bell " attitude, if the wings, instead of 

 being limp and drawn into the bell outline by gravity, 

 were stiff, those of the opposite side would be in nearly 

 the same plane, practically the geometric attitude of rest. 



Pieris rapae emerged at 2.29 (really 1.29 p.m.). 



2.35, wings fully expanded, quite straight, so that 

 they hang with tips only touching. 



