490 Messrs. N. A. Cobb and A. S. Olliff on 



was taken to place them on the lead and not on the wheat- 

 cutting. Finally a glass cover was laid over the chamber, to 

 prevent evaporation, and thus keep the wheat-cutting from 

 withering. The object of the experiment was to ascertain 

 how these little larva? would behave towards the wheat- 

 cutting and the rust-pustule on it. After about an hour, 

 during which time no note was taken of the movements of 

 the larva?, the chamber and contents were placed under the 

 microscope, when all the larvae were found at the rust- 

 pustule, and one of them was unmistakably feeding. The 

 larva took one spore after another, and made very short work 

 of each. It remained uncertain whether other food was 

 taken, but it seemed very improbable. The operations were 

 distinctly seen. 



These interesting facts give rise to the following deduc- 

 tions : — In the first place it could hardly have been acci- 

 dental that all three of the larva after one hour had found 

 their way to the single accessible rust-pustule, which could 

 not have been above half a millimetre in diameter. Their 

 arrangement (one on top of another) was exactly that common 

 to greedily feeding animals. It is therefore probable that 

 the two larva? which were not observed to actively feed had 

 already satisfied their hunger. 



Secondly, it is established that these larva? will, at least 

 under some circumstances, feed on the rust-fungus, apparently 

 in preference to perfectly fresh tissues of the wheat-leaf. 



Again, it must be borne in mind that the larva? experimented 

 with were taken from a rusted linseed plant. This goes to 

 show that it is the rust that is sought rather than the juices 

 of any particular plant. 



Of course these experiments should be repeated and 

 extended ; but no opportunity has occurred to us for this, and 

 it is not likely that they can be repeated until next season. 



We shall endeavour to breed these larva?, so as to obtain 

 the perfect insect. Observations will be made on its habits, 

 with the object of ascertaining more exactly the relations of 

 the insect to rust. If it is found to live exclusively on the 

 rust-fungus, then, so far at least, it is beneficial to the wheat- 

 grower. If, however, it should be found in its wanderings to 

 carry the rust-spores about on the surface of its body, and 

 thus distribute the fungus, it would in that respect be harmful. 

 We have no evidence of this, their bodies having been in all 

 cases found clean and free from adhering spores ; however, 

 not very much attention has yet been given to this latter 

 matter. 



An idea has occurred to us almost purely speculative, but 



