510 Mr. G. Lewis' supplementary note on the 



Later, as the tide ebbed out, the more yielding surface 

 of the sand was exposed, which, being flatter than the 

 beach, and the tide on the wane, the ridges or ripples 

 were much smaller and closer together, and, finally, 

 several ridges and dips could be measured in a span's 

 length. In the ' En. Brit.,' under Light, p. 609, I read, 

 " The scales from the wings of butterflies owe their 

 brightness to a delicate ribbed structure " ; and I believe 

 that light has acted on the wings of Lepidoptera and 

 other living organisms in a very delicate manner, but in 

 an analogous way as the sea did on the sands. The 

 most beautiful butterflies soar with wings stretched out 

 horizontally, and float backwards and forwards under a 

 vertical sun ; while the brown dingy species, flit along 

 hedgerows, with wings half-closed, catching light-rays at 

 all sorts of angles and direct rays very intermittently, 

 and the structural ribs of their scales are modified 

 accordingly. Think of the ripples on the sand and the 

 form they would take in an uncertain, changeable move- 

 ment of the water ; retain in mind the subtle movement 

 of light, the exquisite delicacy of the scales in a butter- 

 fly's wing, and the multitudinous angles the superficies 

 of the wings present to the sun during flight, and we 

 can perhaps account for the varied hues of Lepidoptera. 

 The flight of a Skipper would cause its scales to assume 

 a different structure to those in a Blue, just as a cross 

 movement in the sea would disturb the ridges on the 

 shingle. The same theory will explain also the sexual, 

 generic, and family colours of Lepidoj)tera, for they are 

 dependent on and regulated by the positions of the 

 insects when at rest or during flight ; it will explain why 

 Noctuce have different coloured under-wings, as light only 

 reaches them after passing through the primary ones ; 

 and why Geomctrce have wings concolorous, as all four 

 wings are exposed. Eemarks later on regarding the 

 atmosphere will apply here. And it will show us another 

 thing more puzzling still. 



When insects depart from a type and then again turn 

 towards it, we see forms and colours which surprise us 

 with the similitude they bear to other insects now placed 

 in a classification based on structure, in distant families, 

 and the inquirer is disturbed in his calculations of their 

 affinities. Eor in this way insects which resemble each 

 other in form and colour are often apparently further 

 detached than others less like them. Now we know that 



