INSECTS INFESTING IT. 185 



The insect enemies which vetches have to encounter 

 during the comparatively short period they occupy the 

 land, have been made known to us by Curtis and other 

 entomologists. During the whole period of their growth 

 they are infested by multitudes of insects, the larvse 

 chiefly of inoths, beetles, and flies, which frequently effect 

 great injuries to the crop, whether cultivated for forage 

 or for seed purposes. In their earlier stage, the slugs and 

 snails, with which in some districts and some seasons our 

 fields abound, commit great ravages. At a later period 

 the plants are often visited by a small beetle Phcedon 

 polygoni and its larvse, both of which feed upon the 



I. Portion of a leaf with (2.) eggs. 3 and 4. Larvae of beetle in a young and full-grown 

 I state. 5. Do. magnified. 6 and 7. Beetle ; nat. size and magnified. 



leaves and stems, and do great injury to the crop. This 

 beetle has been noticed in the fields from early spring to 

 midsummer, infesting the docks, sorrel, and knot-grass, 

 whence it moves off to any vetch crop within its reach. 

 It is of a shiny blue colour on the back, with a dark red- 

 coloured thorax, and a greenish blue head, with strong 

 mandibles or jaws for biting. In 1850, entire fields in 

 Cambridgeshire and Hertfordshire were destroyed by 

 this beetle. A peculiar aphis, named the Aphis vicice, is 

 in some seasons abundantly met with, during the months 

 of May and June, on the vetch crop. Curtis also tells us 

 that soon after flowering has commenced the flower-heads 

 VOL. II. 45 



