68 Second Report on Economic Zoology. 



but also radishes. In 1872 it did much harm to them in the Nether- 

 lands ; it is also recorded as spoiling them in Great Britain and in 

 North America (Slingerland). The larvte also live in turnips 

 (Fig. 8, (C) and swedes, and even in horse-radish. In some cases 

 they have been recorded from beans, clover (Ormerod), etc., but in 

 all such cases there has undoubtedly been some error in determina- 

 tion ; for instance, the Bean IJoot-maggot has been shown to be 

 Phorhla /"dsciccps, Zett. 



The Cabbage Eoot-maggot confines its attention to Gruciferx 

 alone, as far as all accurate information and records go (but one 

 exception, viz., Dr. Lintner bred this pest from maggots mining the 

 leaves of beetroots). This is an important point in dealing with 

 the treatment of this pest. As would be imagined, Phorhia Irasdcm 

 does not confine itself to cultivated Cruciferse only, but attacks 

 various wild kinds, as Shepherd's Purse, Charlock, Jack-by-the- 

 Hedge, Wall Mustard, etc. As an instance of its attacking orna- 

 mental plants, the Stock {Matldola) may be named. 



Although this insect is looked upon essentially as a cabbage pest, 

 the damage it does to the turnip crop is often as great as that done to 

 the cabbage. In 1901 swedes were badly injured in Tyrone and 

 County Down, and in County Clare the turnip crop was so badly 

 injured as to be, to a large extent, abandoned (" Journ. Dept. Agri- 

 culture," vol. iii. No. 1, p. 109, Dr. Carpenter, 1902). 



Miss Ormerod (" Manual Inj. Insects," p. 26, 1890) says the 

 maggots are found in dung, but she gives no direct evidence ; none 

 have been seen in dung, and under such circumstances such reports 

 need contirmation before being accepted. I have tried to hatch these 

 larvffi when kept in rank manure, but in all cases they speedily died. 

 That they have frequently been worse where the fields have been 

 heavily manured is no proof that they come with the manure. 



Methods of Maggot Attack. 



The larvffi of the Cabbage Root Fly, as the name implies, mainly 

 live in the roots of plants, but this, as will be pointed out later, is 

 not invariably the rule. 



The first invasion is often upon the seedling plants before they are 

 set out ; in such cases the maggots simply gnaw the young roots, and 

 the plants are killed right away. But usually it is not until the 

 plants are set out that the pest commences its ravages. After feeding 

 •pro tern, on the surface of the roots they gnaw their w^ay into the 

 substance of the roots and tunnel in all directions. The tunnels 

 allow moibture to get into the root and soon cause decay. They will 



