72 TRACTS ON VARIOUS SUBJECTS, &c. 



them ; yet I think the spiky roller would be a means of destroy- 

 ing them. 



The grubs, on which my experiments were made, are, when 

 full grown, about an inch and half long, and a quarter of an inch 

 in diameter. — They are of a bluish colour, and of the moth tribe. 

 This was ascertained by laying their chrysalids upon soil, in a 

 glass covered with thin gause. I have already stated, that on 

 the 30th of October, the second and final transformation took 

 place: the grey moth that was produced measured seven-eighths 

 of an inch in length. — It had two large dim eyes, very near to its 

 mouth, and a feathered like top on its head, lesembling <in owl. 

 One of these months lived in the glass seven days without food. 



It is said, that " all caterpillars of the phaleenae tribe after hav- 

 " ing several times cast their slough, spin their cod, in which 

 " they are transformed into chrysalids :" but the cod of the St. 

 Helena urub is substituted by a crust formed of soil, and the ex- 

 cretions of the insect. Heat, or cold, evidently contributes to 

 forward, or retard, the final metamorphosis. It has been siiewn 

 that the two changes were efl'ected in seven weeks — that is, be- 

 tween the 10th of September and 30th of October. In colder 

 climates, however, they are said to require a much longer time ; 

 and that the greater part do not come forth until the ensuing 

 year. 



The phaleenje, or insects, sprung from those chrysalids, do not 

 possess the brilliance of butterflies ; but what I imagine to be the 

 male moth is more brilliant and active than the female. There 

 is, indeed, a great diflference in their form and colour. The wings 

 of the one are wrapped up or folded round the body ; and those 

 of the other are more spread, and in shape resemble a delta. 

 Some authors have given the moth the name of " night butter- 

 flies ;" — and there seems to be a sort of analogy similar to that 



I 



