INSECTS WHICH PKEY UPOX AGRICULTUKAL PLANTS. 93 



wheat-growing altogether for years on account of its ravages. It 

 is called the " Hessian Fly," from the opinion among the Ameri- 

 cans that it was introduced by the Hessian troops in their straw. 

 The larvae live in families in the sheath of the leaves just above 

 the crown, are of a pale green colour, and one-sixth of an inch in 

 length. The fly is not so large as a common gnat, is of a shining 

 yellowish colour, and clothed with short black hairs. The female 

 lays eight eggs only, in autumn, and the larvae live head down- 

 wards in the sheath of the leaf during the winter, though the 

 mischief done is only discoverable when the wheat is far ad- 

 vanced. They are materially kept in check by the Ceraphron 

 destructor, a minute ichneumon fly which deposits its eggs in 

 the larvae. 



Psila rosce (the Carrot Fly). — The maggot of this fly is that 

 which causes the well-known " rust" on can-ots, tunnellmo- into 

 the roots, and giving the part injured a rusty brown appearance. 

 Th« fly is of a shining greenish-black colour ; the wings lie 

 horizontally on the back when at rest, and extend beyond the 

 tail ; the nervures are a bright ochreous colour. It is about 

 one-fourth of an inch long, and the wings expand nearly half an 

 inch ; the abdomen is furnished with a retractile ovipositor. 

 The maggots are clear^ ochreous, and shining, with a black horny 

 pointed head. They will be found sticking half out of the car- 

 rots when newly pulled, but quickly withdraw themselves on 

 exposure to light. They leave the roots to become pupie in the 

 earth, in which they remain till the spring, though the summer 

 ones emerge in three or four weeks. Liming the soil will help 

 to keep away the flies and kill the maggots, as also a dressing 

 of spirits of tar mixed with sand and sown on the drills, or 

 watering with a mixture of one of carbolic acid to fifty of water. 

 \Yhen the plants are affected it is best to pull them and use at 

 once, being easily known from the withered appearance of the 

 leaves. 



Anthomyia hdce (the Mangold Wurzel Fly). — The maggot of 

 this insect is well known as the one which mines out the cellular 

 tissue of the leaf and produces the blistered appearance on it. 

 It is of a greenish colour, one-fourth of an inch long, and pointed 

 at the head ; it turns to a pupa in the leaf resembling that of 

 the turnip fly. The imago is about the same length, of an ashy- 

 grey colour, with black bristly hairs, and striped longitudinally 

 on the trunk. It is rarely that any great damage is done 

 to the plant, though j)Ossibly the allected leaves may injure 

 cattle. The only way to check them is by squeezing the maggot 

 between the finger and thumb, the blistered spots on the loaves 

 being easily seen ; though it is of course out of the (juestion to 

 do tliis on a large acreage. 



AntJiomyia hrassiccc (the Cabbage Fly). — The maggots of this 



