Observations on Insects- affecting the Turnip Croj)s, 73 



are of a purplish brown, the latter is crested; the wings when at 

 rest are closed and a little deflexed ; the superior are somewhat 

 lance-shaped, shining like satin, of a dull blossom colour with a 

 slight coppery tinge, and beautifully variegated with brown and 

 grey, and at the centre is a pale golden letter like the Greek 7 ; 

 the body and inferior wings are smoky ; the former has a few tufts 

 of scales on the back near the base, and the latter are often of a 

 whitish blossom-colour across the centre, leaving a broad brown 

 margin; the fringe is whitish, with a line of blackish spots: it is 

 I of an inch long and more than IJ inch in expanse. 



From the green colour of the caterpillars they are difficult to 

 detect : yet they must be very abundant, from the immense quan- 

 tities of the moths we see flying about fields, hedges, heaths, and 

 gardens, from the early spring until the end of autumn, but they 

 are most abundant in July and October. It has been remarked 

 in France that rainy seasons seem to be more favourable to their 

 increase than dry years ; and in October, 1816, they rose in swarms 

 in the northern departments, as persons walked over the fields.'^ 

 In 1735 the caterpillars did incredible mischief to the market- 

 gardens around Paris, eating up the peas and beans, so that only 

 the stalks and fragments of the leaves were left, and refusing 

 nothing but the lentils : their ravages extended to Tours, and in 

 Auvergne and Burgundy they destroyed the crops of hemp ; and 

 not only did the gardens suffer, but whole fields of culinary plants 

 were consumed, and so great were their numbers that at any one 

 time several scores and more could be seen in the highways going 

 from one field to another in search of food,f where they would not 

 refuse either clover or grasses, but they did not touch either 

 wheat, rye, or barley, although later in the season they attacked 

 the oats. 



These extraordinary swarms of insects, and their irregular re- i>^ 

 turns, may be sometimes owing to the mildness of the foregoing 

 winter: in the instance just related, there had been no severe 

 frosts either in the winter or spring, so that the previous autumnal , 

 broods of caterpillars lived through the cold season, and it neces- 

 sarily followed that an immense number of the moths were pro- 

 duced, and the spring and summer which succeeded proving favour- 

 able to their increase, they became more abundant than they had 

 ever been known before. It is only surprising that such events 

 do not oftener occur, when we consider the rapidity with which 

 insects increase. Let us, for instance, suppose that no accident in- 

 terfered with the progress of the different broods of this moth, of 

 which there are two every year : it is believed that one female moth 



* Godart's Lepidop. de France, v. 7, part 2. p. 43. 

 t Reaumur, Hist, des Ins, v. 2, p. 326. 



