234 APPENDIX. [No. XV.B. 



moss, too, is considered to be very nutritive, as given to consumptive and 

 debilitated persons ; therefore I had some bread made from Iceland moss, 

 but it turns out to be a complete failure, for it is so intensely bitter that it 

 cannot be eaten ; indeed, it is quite as bitter as either quinine or Peruvian 

 bark. These investigations in reference to the scarcity of food have 

 occupied much time when my other engagements have been numerous and 

 pressing, and several other subjects have had their consideration neces- 

 sarily postponed by them, but I have always received the utmost kindness 

 from all quarters in carrying out my inquiries. 



At this moment the room was darkened, when Mr. Smee gave an 

 interesting description of numerous preparations of aphides in their 

 different stages of existence, of the various insects which prey upon them, 

 and of a number of specimens of diseased potatoes, and other plants, with 

 various fungi, and also of living aphides, &c. &c., all of which were 

 exhibited by means of a powerful oxyhydrogen microscope, manufactured 

 by Messrs. Home and Thornthwaite, of Newgate Street. This part 

 was most highly applauded, and the whole produced considerable sen- 

 sation. 



Objects shown under the microscope : 



Eggs of aphides ; larva ; pupa ; and perfect Aphis vastator. 



Aphis lanigera, which infests apple-trees. Sir Joseph Banks has 

 given a description of this, and states that it has damaged one orchard to 

 the amount of 50 per year. 



Couch-grass aphis, fox-tailed. 



Aphis, called the black collier, taken from the beet-root. 



An ordinary green-fly, having long legs, &c., and being very different 

 from the vastator. 



Rose aphis. 



Pea aphis is very destructive to peas, which were destroyed partly by 

 this insect, and partly by the dry summer, last year. 



Barley aphis, with its wings in repose. 



Grass aphis, by which whole tracts of grass were destroyed last 

 year. 



Willow aphis, which is one of the largest of the family. 



"Wheat aphis is two or three times as big as the vastator, which, how- 

 ever, also lives on the wheat. 



The nut-bush aphis is very small. 



(?) Hycemal aphis; the large black spots which are a fungus on the 

 leaf probably follow this aphis. 



Cabbage aphis ; the cabbages brought to market last year were covered 

 by this white downy aphis. 



Many aphides secrete sugar, and in honeydews this is very obvious. 



Ichneumons, or hymenopterous insects, from the swollen aphis. 



Another ichneumon with a round body. 



Various others found about potato-fields. 



Red acarus, about the size of a large spider, and which eats aphides 

 very voraciously. 



Minute acarus. 



