FLIGHT-FUNCTION IN THE SILKWORM, 121 



eration on the basis of its being " functionally degenerate,"^ and 

 psychologists allude to the non-flight habit as indicating a loss 

 of the " flying instinct." ^ 



Especial interest therefore attaches to the fact that this appa- 

 rently useless organ persists in a perfect form and under perfect 

 muscular control. 



Though slightly variable in the character of its venation, as 

 pointed out by Kellogg and Bell, we do not know that the veins 

 vary more than in the wings of moths of other species, and in com- 

 paring the wings of along series of "non-fliers" with those of 

 " fliers " I find no structural differences between the two lots. The 

 wings appear, however, to be fundamentally non-useful, since 

 both effectual mating and effectual ovipositing, the only adult 

 activities, can be successfully accomplished without them. The 

 de-winged silk-worm moth exhibits no inconvenience in these 

 respects. Mayer-Soule ^ found that in certain species males de- 

 prived of wings met with greater resistance from females when 

 the females were deprived of sight. The female silkworm moth, 

 however, exercises no selection between the normal and de-winged 

 male, nor does the male between normal and de-winged female. 



Although the wings are normally not used in flight, as pointed 

 out, they are habitually fluttered preliminary to mating. This 

 fluttering of the wings may effect a circulation of the air in the 

 neighborhood of the moths so that the presence of the female 

 with extended scent glands is more readily discerned by the 

 male. However, the natural proximity of males and females 

 under the usual conditions of silkworm breeding renders this use 

 of but little importance. 



The wings are also made use of in the "turning reflex." A 

 moth placed upon its back instantaneously rights itself by 

 bringing the forewings quickly together and thus exerting a 

 pressure upon the surface. This procedure follows in the decapi- 

 tated as well as in the normal moth, and though one rarely neces- 

 sary under usual conditions it shows the perfect muscular and 

 nervous control under which the wings are held. 



^Kellogg and Bell, "Inheritance in Silkworms," I., Stanford Univ. Pub., No. 

 I, 1908. 



^ Oppenheim, " Mental Growth and Control," 1902, p. 99. 



^ Mayer-Soule, " Some Reactionsof Caterpillars and Moths," Juttr. Exper. Zool.y 

 Vol. III., 1900. 



