MUSTARD. MUSTARD BEETLE. 



151 



Millepede, J. terrestris, with the note that a few mornings 

 before he had noticed the Millepedes in great numbers cross- 

 ing a road from a field of Oats towards a pasture-field. The 

 Oats were after Turnips (both crops partially failures), and 

 the manure had been of a mixed sort suitable for encourage- 

 ment of the pests. This power of migration would account 

 for the very sudden appearance of attack in full force — for as 

 Millepedes live for two years before they are full-grown, it 

 may be presumed when a sudden devastation is set on foot, 

 that they have suddenly arrived — for there is no sudden change 

 in their powers, and if present previously in the warm season, 

 they could not fail to have been feeding up to the date of 

 observation.* 



MUSTARD. 

 Mustard Beetle ("Black Jack"). Plutdon bctula,lAiva. 



Phccdon hctulce : 1, 3, 4, larva (natural size) on leaf; 5, larva (magnified); 

 6, beetle, natural size ; 7, beetle, magnified ; 2, eggs. 



The beetle, which is especially known as the Mustard Beetle, 

 is the Phcedon hetulce, Linn., formerly known as Chnjsomela 

 hetidce (figured above, natural size and magnified) . It is oblong- 

 oval, hardly the sixth of an inch in length, of a full blue or 

 deep greenish colour above, and so brightly shining as to be 

 of an almost glassy lustre. The legs, horns, and body beneath 

 are black. The thorax or fore-body is very minutely punctured, 

 the wdng-cases having punctured striae, with the spaces between 

 the striae also punctured. 



* For Beet Carrion Beetle, which is sometimes very destructive to Mangolds, 

 see this heading. 



