264 ON AILANTHINE. 



Which leaves a balance of 7915 frances for the twelve acres, or in 

 round English numbers, £330 for twelve acres, or £21 10s. per 

 acre. In India and China there are said to be six crops of silk 

 annually ; in the south of France two or three crops, but in the 

 north of France and Great Britain two at most, and more securely 

 one crop might be relied on. Let us take one good crop and see 

 how our profit and loss account would stand in Great Britain 

 The half of £21 10s. or £13 15s. would be the result, or about it; 

 and be it remembered, for land, that after the planting of the 

 ailanthus it requires no manure or tillage whatever, and the kind of 

 soil being that on which nothing else would grow, provided always 

 that it has as sheltered and suuny an exposure as possible. It 

 always occurred tome that the climate of Canada would be espe- 

 cially favourable for the growth of ailanthine. The insect and the 

 plant on which it feeds will stand any amount of cold ; and when 

 the Canadian summer would arrive, rapid growth would take place 

 in the tree, followed by hatching of the worm ; in this way food 

 would be speedily produced for the young brood, and two if not 

 three crops of silk taken from the trees during the season. The 

 experiment is one worthy of trial. 



In England and Scotland, for the last two years, some, experi- 

 menters have been at work but as yet. without any quantitative 

 result. In the spring of 1862 I received, through the kindness of 

 a friend, fifty eggs of the Bombyx Cyrthia ; they hatched in 

 about ten days after their arrival ; they were fed with cut branches 

 of ailanthus ; kept in the ordinary temperature of the atmosphere* 

 but under glass. Of the fifty worms (for the eggs all hatched) 

 with all my inexperience, I had thirty-five large and fine cocoons 

 being a result not far short of that in the central districts of France. 

 With more experience and with growing plants prepared for the 

 trial, I do not fear for the result of a quantitative trial in Scotland 

 at any future year. 



It is my intention, in describing this insect, to follow the differ- 

 ent changes which it undergoes from the egg onwards until we 

 arrive at the characterizing moth itself,from which distinctive marks 

 and pecularities are chiefly taken. 



The Eggs. These are about the size of a large pin head, twice 

 as large as those of the mulberry silk-worm with which we are 

 all familiar. They are yellow coloured, equally large at both ends,, 

 flattened from above downwards, and with a depression in their 

 centre. They soon change their colour to a o-reenish black, the 



