23 
Prof. Westwood asked whether Mr. Wallace had observed the twisting or 
“dodging” flight to be conspicuous in the butterflies which have largely-developed 
wing-tails ? or whether the tails contributed to or affected the flight in any, and, if 
any, in what manner? 
Mr, Wallace replied that he had not observed that the wing-tails had any influence 
upon the flight of the insect; he did not think they affected the rapidity, or that they 
acted as a rudder, and he was at a loss to assign any use to those appendages. With 
respect to the other puints which had been touched upon, there was in some cases an 
increase of muscular power as well as an*increase of curvature of the wings, but the 
wing of a butterfly was far more liable to variation than the body of the insect; that 
organ was therefore more accessible to the operation of the principle of selection, and 
a modification of its form was consequently more readily produced. Most of the 
instances of swift-fliers with straight wings which had been adduced (as e.g. the 
Sphinges) were insects with the strongest bodies and the greatest muscular power; 
moreover, he did not maintain that any insect with arched wings would have a more 
rapid flight than any other with straight wings; all that he had argued was, that, as 
between two closely allied species, the one which had the wings most arched would 
have the flight most rapid ; for instance, he should expect a Sphinx with arched wings 
to fly more rapidly than a Sphinx with straight wings. But in truth, though he had 
referred to the supposed concomitancy of faleate wings and a rapid flight, his own 
notion was (as had been correctly stated by Mr. Baly) that the arched form was 
chiefly useful in giving greater power of turning or twisting. As to the enquiry 
whether he had seen the butterflies actually pursued, he admitted that he had not to 
any great extent; he offered his explanation as a theuretical one; but he thought it 
could scarcely be doubted that butterflies were subject to the attacks of numerous 
depredators. 
Paper read. 
The Secretary read a paper, “ On the Reversion and Restoration of the Silkworm,” 
by Captain Thomas Hutton, F.G.S., of Mussooree, N.W. India. 
The author attributed the enormous loss of silkworms by “ muscardine” and other 
diseases, and the consequent diminution of the crop of silk, to the combined effects of 
bad and scanty food, want of sufficient light and ventilation, too high a temperature, 
“and constant interbreeding for centuries of a debilitated stock. He asserted that there 
was no such thing now in existence as a perfectly healthy domesticated stock of silk- 
worms; and moreover, that it was useless to seek for healthy seed, for whether in 
Europe, Persia, India or China, the worms were all equally degenerated, or, if there 
were a difference at all, it was in favour of the European race. He had for several 
years been experimenting upon Bombyx Mori, with a view, if possible, to reclaim the 
worms, to restore to them a healthy constitution, and to induce them to revert from 
their present artificial and moribund condition to one of vigour and permanent health. 
The occasional occurrence in a brood of one or more dark gray or blackish-brindled 
worms—the “ vers tigrés” or “ vers zebrés” of the French—contrasting strongly with 
the pale sickly hue of the majority, must have been noticed by all who have had 
experience in rearing silkworms; such occurrences have been always spoken of as 
indicating variety arising from domestication. The author had endeavoured, by a 
series of experiments, to ascertain the cause of this phenomenon, his conviction being, 
either that the species had at some time or other been crossed by another of different 
colours, and that Nature, as sooner or later she always would do, was making an effort 
