On Insect-Larva eating Rust on Wheat and Flax. 489 



When time is ripe for that, I venture to hope that it will not 

 be necessary for my very friendly antagonists to lay so much 

 stress upon misrepresentation. 



LVI. — Insect-Larva (Cecidomyia, sp.) eating Rust on Wheat 

 and Flax. By N. A. Cobb and A. Sidney Olliff*. 



On many specimens of rusted wheat received from various 

 parts of New South Wales we have noticed an orange- coloured 

 larva. Our attention was first called particularly to these 

 larva? by the fact that they were invariably more common on 

 the rusted plants. The orange colour of the larger of these 

 larva? would naturally suggest at once some connexion 

 between them and the rust, which is also orange-coloured. 

 This, in fact, had already been the case, one farmer averring 

 most positively that these larva? were the cause of the rust. 

 This conclusion, founded on colour resemblance alone, could 

 have little, in fact almost no weight, and we were inclined to 

 regard the colour as deceptive, like the red coloration on fence- 

 rails, and felt ourselves fortified in that position by the know- 

 ledge that these larva? were probably Cecidomyia larva? and 

 would very likely be found to live on the juices of the wheat- 

 plant. Later, however, specimens of rusted linseed were 

 received, and on these also the same orange-coloured larva? 

 were found. We say the same, because on placing them 

 side by side with larva? from rusted wheat we could detect no 

 difference. If these larva? fed on the juices of plants, it was 

 somewhat remarkable that the same species should be found 

 on such different plants as wheat and flax. On the other 

 hand, both these plants, though widely different from each 

 other, were attacked by a rust in its Uredo- stage, and the 

 Uredospores of the rust were very similar. This fact led to 

 the suspicion that the rust-spores might be the food of the 

 larva? and to the following experiment. A moist chamber 

 was partly filled with water, and in the midst of the water a 

 piece of lead was so arranged as to form a miniature island 

 about one fourth of an inch across. A fresh cutting was then 

 taken from a wheat-leaf in such a manner as to include on its 

 surface a single Uredo sorus. This cutting, one eighth of an 

 inch wide and one quarter of an inch long, was placed on the 

 miniature island together with three larva? of the Cecidomyia. 

 The larva? were taken from a rusted linseed plant, and pains 



* From an advance proof, communicated by the Authors, from the 

 ' Agricultural Gazette of New South Wales,' vol. ii. part 2. By authority. 

 Sydney, 1891. 



