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whilst on the wing, yet, when settled, you may lay your net over it with little 

 trouble/' 



Moses Harris, in his " Aurelian," published in 1775, writes " On the 26th 

 of May, in the year 1758, Mr. Drury, an ingenious Aurelian, in searching 

 for caterpillars, beat four off the sallow near Brentwood, in Essex ; which in 

 their shape and motion differed from any hitherto discovered, being furnished 

 with two horns, of the same hard substance as their heads, resembling the 

 telescopes of a snail, and in their progressive motion seeming rather to glide 

 along like that animal, than crawl as most caterpillars do. Struck with the 

 oddity of their appearance, and knowing I was about a work of this kind, lie 

 was so obliging to give me one of them, which 1 fed on sallow, and found, 

 that excepting the above-mentioned particularities, it greatly resembled the 

 hawk tribe, having a point or horn in its tail, its body being green, beauti- 

 fully frosted with minute yellow specks, having likewise seven diagonal lines 

 of a pale yellow on its sides, and when at rest generally sitting in the posture 

 these caterpillars do. On the sixth of June, at night, it changed into a chry- 

 salis of a beautiful pea green, with a bloom of pearl colour on it, and what 

 is more remarkable, the diagonal lines, which crossed the sides of the cater- 

 pillar, are seen in this state, though the colour is fainter. This being the 

 chrysalis of one of the finest flies in this part of the world, Providence 

 seems to have taken peculiar care for its preservation in this defenceless 

 and tender state, by making its colour so like the leaf it hangs on to, that it 

 might escape the search of a very nice eye. In examining that part of the 

 chrysalis which contains the wings of the fly, I was confirmed in my opinion 

 of its being the Purple Emperor, by observing that the square points of the 

 under wings projected beyond the rounded extremity of the upper ones; 

 this conformation of the under wing being peculiar to that fly. On the 22nd, 

 at night, a few dark spots were visible on the wings, and the next day I 

 found more on different parts of the body, which spread gradually till the 

 whole fly appeared black through the transparent chrysalis, and about 

 eight in the evening, to my unspeakable pleasure, it produced the 

 male Purple Emperor. Here I hope 1 may be indulged in expressing my 

 gratitude to my generous and worthy friend Mr. Drury, for the discovery of 

 the caterpillar of one of the most beautiful flies in the Universe, and which 

 had hitherto eluded the search of the most skilful and industrious Aurelians. 

 The colour of this fly is changeable, according to the different lights it is 

 viewed in. For in one it appears of a sooty black, and in another the eye is 

 suddenly dazzled with a resplendent glow of fine purple; so that by fre- 

 quently turning the fly into different positions, the colours play and shift 

 through all the gradations, from a sooty black to a bright purple, in such a 



