902 PHOCEEDINGS OF THE THIRD ENTOMOLOGIC.M MEETING 



Experts in camouflage will probably be able to form an opinion as 

 to how far the inconspicuousness of demohus when in fast flight is due to 

 its colouring and how far it is due to its speed. It is in fact a fast- 

 flying butterfly. If it is considered possible that the pattern is one that 

 makes for invisibility, experiments with low-flying aeroplanes similarly 

 coloured might give results of scientific interest and possibly of practical 

 utility. 



A singular change in the colouring of demolcus takes place with age. 

 At the beginning of the monsoon season the only specimens seen flying 

 are survivors from the previous season. In two or three specimens 

 that I have examined in this condition the dark ochre-yellow of the 

 under-surface has faded to a tint not markedly different from the yellow 

 of the rest of the wing. But, as though in compensation, the yellow of 

 the upper surface has greatly deepened. The red spot had faded on the 

 under siu-face but not on the upper side. It seems jDrobable that the 

 fading of the under surface tends to reduce conspicuousness when the 

 insect is hidden and at rest during the cold and dry seasons of the year. 

 The hind wings of these old specimens are very frecjuently damaged as 

 though from the attacks of birds. 



A second butterfly is found in Agra that is somewhat markedly 

 incon,sjDicuous when in flight. Its name is Jmionia lemonias. It differs 

 in its flying habits from P. demole>is in that it generally flies at a height 

 of about a foot or two above the ground. A bird that was chasing it 

 would probably keep on a higher level and would therefore see more of 

 the upper sui'face of its wings, especially as when flying it often makes 

 short glides with its wings in the horizontal position. It is of interest 

 to notice that the upper siu'face of each wing of this butterfly has a large 

 eye-spot of blue, black and orange brown that recalls the colouring of 

 the spots on the underside of P. denwleus. 



Note. — The substance of the above remarks was communicated to the Comptroller 

 ofMunitions Inventions, who forwarded my letter to the Camouflage School in Kensing- 

 ton. A report received therefrom stated that the upper wing of the insect (Pupilio 

 (hmoleus) was photographed. The pattern was cut out of the resulting print and the 

 parts weighed. The weights thus obtained gave the proportions of the component 

 colours. The colours were then exactly matched and painted on a spinning wheel in 

 the same proportion as occurs in the wing of the butterfly. Both surfaces of the wing 

 were treated in this way. On spinning the wheel the resulting colours were for the upper 

 surface a moderately dark olive green and for the lower an earth colour. Spinning 

 these two colours together, as would occur when the insects wings are blurred in flying, 

 was found to result in a khaki colour. 



" It is also noteworthy," the report states, " that this colour almost e.xactly matches 

 one of the colours found most useful in the concealment of low-flying aeroplanes from 

 overhead observation." 



Dr. Hankin's paper is an excellent example of the fact that even the 

 coumionest of insects repay study. Papilio demoleits is an abundant 



