232 THE WOODLANDS. 



of species inhabiting a district is found to be governed, 

 as might be supposed, by the varied character of its 

 flora. Some aphides affect timber-trees exclusively, 

 others feed on soft, succulent vegetables and low 

 herbs ; others again infest the roots of grasses, or hide 

 under stones and the rotten mortar of old walls, &c. 



Although certain trees, as the lime, &c., appear 

 to be attacked exclusively by their particular aphis, 

 other trees give shelter indiscriminately to numerous 

 species. Thus, the oak is infested by at least six, the 

 birch and willow by eight, the elm by four, the fir 

 tribe by eight, and the currant bush by three different 

 species. 



In times past much has been conjectured and 

 written about " honeydew," a sweet secretion, which 

 is found in summer freely sprinkled over the upper 

 surface of the leaves of various trees, notably of the 

 lime and the sycamore. Some held it to be an exuda- 

 tion from the plant, others as a secretion exuded by 

 aphides, and, more ancient still, that it was nectar dis- 

 tilled from the skies. It is now generally conceded that 

 the honeydew as found upon leaves is derived from 

 these insects, which is strengthened by the following 

 memorandum from the note-book of an observer : 

 " Bright, sunny morning ; the under-sides of the oak- 

 trees well tenanted by winged and apterous females of 

 an oak aphis. The upper surfaces of the leaves of 

 the Portugal laurels, growing under the oaks, are 

 freely sprinkled with shining spots of honeydew. On 

 gently touching one of the winged females, the abdo- 

 men was raised, and a bright particle, easily seen in 

 the sunshine, was projected from the summit of one 



