218 INSECT TRANSFORMATIONS. 



so numerously as to threaten the entire destruction of 

 . fruit trees, including the cherry, plum, pear, and 

 quince. Where they are numerous, the air becomes 

 loaded with a disagreeable and sickly effluvium. The 

 history of this orchard pest has been admirably 

 written by Professor Peck.* 



When a turnip crop has been fortunate enough to 

 escape the ravages committed on it in the seed leaf 

 by a small jumping beetle (Haltica nemorum, ILLI- 

 GER), and by a root weevil (Nedyus contractus, 

 STEPHENS), a no less formidable depredator some 

 times appears in a caterpillar belonging to the saw- 

 fly family (Tenthredinidce}, and apparently of the 

 genus Jfthalia. An instance .is recorded by Mar- 

 shall, in the Philosophical Transactions, of many 

 thousand acres having had to be ploughed up on 

 account of the devastations caused by these insects. 

 It is, he informs us, the general opinion in Norfolk, 

 that they come from over-sea; and a farmer averred 

 that he saw them arrive in clouds so as to darken 

 the air, while the fishermen reported that they had 

 repeatedly witnessed flights of them pass over their 

 heads when they were at a distance from land. On 

 the beech and the cliffs, indeed, they lay in heaps, 

 so that they might have been taken up with shovels; 

 while three miles inland they crowded together like 

 a swarm of bees.")" 



We have little doubt, however, that these details 

 are put in an inverse order; as frequently occurs in 

 histories of the proceedings of insects by those but 

 little acquainted with their habits. Insects of this 

 family, indeed, seldom fly far, and could not at all 

 events cross the sea, unless it might be a narrow bay 

 or inlet; and if they had, we ought to have heard of 

 their departure as well as their arrival, since their 



* Nat. Hist, of the Slug Worm, Boston, 1799. 

 i Phil. Trans, vol. Ixxiii, p. 317. 



