GBAMINEOUS CROPS. 99 



(4) The Parasites op Oats {Avena sativa). 



Aphis granaria, Cephus pygmceus, Tylenchus devasta- 

 trix, Tylenchus Havensteinii, and various wireworms 

 (wHch have already been described) attack Avena sativa. 



The Frit Fly (Oscinis vastator, Oscinis frit) is 

 a small dipterous insect wliicli attacks barley and wheat, 

 as well as oats. This fly caused serious damage to the 

 oat crops of 1887. It is about 2f' lines,i or a little more 

 than i of an inch, in length, with a blackish head, thorax, 

 and abdomen. The feet are yellowish, while the halt^res 

 (or the rudiments of the posterior wings of other insects) 

 are of a light buff colour. The female fly lays white eggs 

 on the leaves of the above-mentioned crops, from which 

 white grubs make their appearance in a short time. The 

 grubs (like those of Chlorops tceniopus, Cephus pygviceus) 

 infest the stems of and live upon the soft tissues and juices 

 of corn plants. The grubs of this fly are about j inch 

 long, and are devoid of legs. They turn to pupae of a brown 

 colour ; and, according to Dr. Nordlinger {Die Kleinen 

 Feinde der Landwirthschaft), the pupae may hibernate 

 on grasses or in the earth. There are several broods 

 during the summer. In Prance, Germany, and especially 

 in Sweden, the grubs live on " the growing grain," as well 

 as infest the stems of the host-plants. The ravages of this 

 farm pest are greater during a dry than a wet season. 



Prevention. — After oats or any other corn crop has been 

 infested with this insect, ploughing up the land has been 

 recommended as a preventive against a subsequent attack 

 during the next season. 



Cure. — It has been suggested, that before sowing oats 

 infested with the brown pupae of this fly the seed should 



' 1 line=j'j inch. 



