ioi'8 



Mustard Beetles. 



[march, 



in mid-June, 1904, adult beetles were sent from Bath, where 

 they were destroying a bed of watercress. 



The adult (Fig. a) is broadly oval, and measures just over 

 J- inch in length. In colour it is shining metallic blue or deep 

 green ; the antennae, legs, and under-surface of the body are 

 black. Fowler adds as characteristic, "anal segment of the 

 abdomen with a broad and bright reddish testaceous border." 

 The thorax, narrower in front, is markedly punctured. The 

 wing-covers also show many punctures, these punctures being 

 not only on the lines or striae that run down the wing-covers, 

 but also in the spaces between the striae. 



The larva, or grub (Fig. b), is smoky or dull yellow in 

 colour, spotted with black, and is somewhat hairy ; the head is 

 black ; the legs are six in number, and are black, but there is, 



in addition, a muscular process at the hind end. Along each 

 side of the body is a row of tubercles, brown in colour ; from 

 these tubercles yellow glands can be protruded. The length 

 of the grown grub is about J inch. The grub newly hatched 

 is bright yellow, but the colour becomes dull. 



The adult beetles pass the winter in many different shelter- 

 places at and in the neighbourhood of fields where the grubs 

 have been at work — in such shelter-places as mustard stubble, 

 hollow stems of wild plants, rubbish-heaps, at the base of 

 rough grass, under bark, and in cracks in gate-posts and 

 fences. 



Issuing from their winter quarters in spring, the beetles 

 lay their eggs on the under-sides of the leaves of mustard; 

 the eggs are yellow. The grubs feed on the leaves, and many 

 can be found on a single leaf. Adult beetles have been sent 

 to the Board in May, June, July and August. The grubs, 

 when full grown, drop away from the food-plants to the 



Description of Beetle. 



Mustard Beetle {Phaedon betulae). 

 a. Beetle x 3 ; b, Larva, x 3. 



Life-History . 



