ON AILANTAINE. 265 



colour becoming more marked the nearer the point of hatching is 

 at hand. The caterpillars are hatched from ten to fifteen days 

 after the eggs are laid according to temperature. 



The Caterpillar. When the worm first escapes from the egg it 

 is exceedingly minute ; the colour of the segments of its body at 

 this early stage is obviously yellow, but there are so great a num- 

 ber of black spots and dark coloured tubercles over it, as to give 

 the impression that it is of a black colour ; during the second period^ 

 that is to say after the first change of skin, the yellow colour 

 becomes more marked, but the spots and tubercles are still black. 

 During the third period, they become nearly pure white, arising 

 from the presence of a white mealy secretion over their bodies, 

 destined, obviously, to protect them from rain or dew, as water 

 will not fix on it; the spots and points of the tubercles are still 

 black or bluish black. 



During the fourth period the body is at first white, but gradu- 

 ally changes to a pale green, the tubercles assuming the same 

 colour, and soon the head, the feet, and the last segment become 

 of a golden yellow ; the flowery secretion still, to a certain extent, 

 exists, and there are always black points upon the segments or rings 

 of the body. 



During the fifth period the emerald green colouring becomes 

 more intense, the points, as to segments, assume a soft black 

 colour, and the extremities of the tubercles a marine blue. The 

 caterpillar grows rapidly during this stage, eats largely and greed- 

 ily till it attains the length of from 2f to 3 inches long, it then 

 ceases to eat, becomes torpid for a few days, and then, after fast- 

 ening a few leaves together at the extremity of a leaf or branch it 

 begins its cocoon. Such is the general character of the changes 

 which this caterpillar undergoes ; but to enable those who may 

 follow out this inquiry to know when these changes may be ex- 

 pected and the size of the animals in them I will give a short 

 table of my own experience, and that of my friend Dr. Gudwad, 

 both in Scotland : — 



Eggs hatched, 28 to 30th June size f of an inch. 



First change, 1 to 9th July size \ of an inch. 



Second change, 13 to 15th July size 1 inch. 



Third change, 20 to 22nd July size \\ inch. 



Fourth change, 28 to 30th July size \\ to 2 inches. 



From this time till the period when it begins to spin it rapidly 

 grows till it reaches from two and a half to three inches long, 

 depending upon the abundance and quality of its food. 



