310 PORTIONS OF A LETTER, &C. 



day it had been sowed. There was no speck of green for the 

 eye to rest upon. It was a wild and universal desolation, and the 

 black crawling vermin that had caused the ruin were clustered 

 in bunches on the ground, and on the remnants of the turnips, 

 and were dying of starvation. No plague of Egypt could 

 have been more effective : the mischief was complete. Some 

 few fields received the blast a few days later than others, but 

 all had it ; not one escaped unless the crop were Swedes, and 

 it is remarkable that these were untouched. I need not tell 

 you that I boxed some of the grubs, to learn something of 

 their history, but have not progressed in the affair yet. I am 

 certain the grubs are the produce of the fly ; the eggs were 

 laid on the young leaves of the turnips, and hatched and 

 turned into grub. The build of the grub proves beyond a 

 doubt that it is the larva of the fly. It is rather rough coated, 

 but without hairs ; it is of a dull leaden sort of black colour, 

 and has a lighter line along each side ; it has twenty feet. 

 It is fond of resting on the leaf curled up in a ring, and if 

 disturbed tumbles on the ground without opening ; indeed, if 

 not in a ring before, it rolls itself into one when touched. 

 I send you a pen and ink sketch both of the grub and fly. 

 The grub is the natural size; the fly is of the length and 

 breadth of the cross below it : the parts I have left white are 

 yellow. I think I have done it accurately enough for you to 

 tell me the name. b I find, on referring to the accounts of 

 the enemies of turnips, that these blacks were well known 

 formerly, but the race seems to have become extinct and 

 forgotten. I find a hundred recipes for their destruction, all 

 of which are moonshine, except one, which is for a wonder 

 rational. It is this : — buy an immense lot of ducks, and turn 

 them in your turnips, and they will devour the grubs by 

 millions, and become in a few days as fat as butter. Thus 

 two birds are killed with one stone — the ducks fatted and the 

 turnips saved. When we get on a little further with our in- 

 quiries into the history of animals, especially such little things 

 as insects, you may depend upon it we shall find the best way to 

 check the increase of any hurtful kind is to encourage any other 

 animal, beast, bird, fish, or insect, that makes the injurious 



b The insect described is the Alhalia spina) urn of most entomological cabinets, 

 but is described by Stephens as the Tenthredo ceniifolhc of Panzer ; Athalia 

 centifolia, Stephens. 



