248 DIPTERA OR TRUE FLIES. 



which the flies come from the end of June to the eml of July. 

 The second brood after hatching out sometimes attacks the 

 corn, laying its eggs in the oar. One instance of this attack 

 in barley has come to my notice in Britain. The later hatched 

 ones live as larvte in wild grasses, and having matured are ready 

 to attack the oats in the spring. This disease is often found 

 combined vcith an attack of Tulip Eoot {T[/lenchtis), p. 80. 



Previ'ntion and Remedies. — In some cases where the whole 

 crop is badly attacked it is advisable to plough it up. Should 

 this be done, it is important to plough in as deeply as possible, 

 so as to effectually bury the insects, which speedily hatch out. 

 If on the first signs of attack we use stimulating manures, we 

 can still get a good crop, the healthy plants tillering out over 

 the space left by the dying ones. 



FA.MlhY PSILID^. 



The Caurdt Fly (Psila ros.e). 



Every one who takes an interest in the garden knows the 

 disease called " rust " in carrots. Rust is due to the larvae of 

 one of the flies belonging to the family PfiiUdu: The Carrot 

 Fly {Pdla ros(ii) (fig. 142, 7 and 8) is a small fly less than half 

 an inch in expanse of wing, of a shiny metallic green colour, 

 with a large yellow bead, black eyes, and yellow legs ; the 

 wings are iridescent, and the veins yellow. The flies appear 

 about the time the young carrots are up, and lay their eggs 

 close down upon the plants; the young larvas coming from 

 them are long pale yellowish maggots pointed at the head end. 

 They are white when quite young, and at once eat their way 

 into the carrot, where they tunnel about at first under the rind, 

 then internally, and cause rusty patches to appear over their 

 abode. The tip of the carrot is often first attacked. On 

 pulling up a carrot showing outward signs of this attack, one 

 may find several of these larva; half out of the carrot (fig. 142, 



