VOL. LXI.] PHILOSOPHICAL TRANSACTIONS. 125 



two after their intercourse with the males, are observed to lay their eggs; which 

 they usually do near the buds, when they are left to their own choice. Where 

 a number are crouded togetlier, they of course interfere with cash other; in 

 which case, they will frequently deposit their eggs on other parts of the branches, or 

 even on the spines with which they are beset. He does not however find that the 

 eggs priKluced by these insects hear any proportion to the number of young ones 

 which proceed from the females of other generations; not having observed any 

 one insect to produce more than 2 or 3, and that in appearance with great 

 difficulty. 



Having now traced their progress through the different seasons of the year, 

 and observed the various metamorphoses which they successively undergo; Dr. 

 R. cannot help suspecting the insufficiency of human reason, in setting any 

 scheme to which the different changes of insects may be accurately reduced. 

 Though the indefatigable Swammerdam seems to have been fully convinced that 

 there is no insect, whose changes may not be reduced to one or other of the 4 

 orders he has described; still the insect now under consideration, having at dif- 

 ferent seasons quite different appearances, cannot, Dr. R. thinks, with strictness 

 be confined to any of them. In the spring they seem in some measure to coin- 

 cide with the first order, though in summer those with wings more properly be- 

 long to the 2d; but in autumn, the males may seem to come under one order, 

 and the females under another; or, he rather thinks, these insects are not clearly 

 reducible to any order. 



Sect. 4. — Some o( the insects now under consideration continuing to lay their 

 eggs till the beginning of November, Dr. R. chose to defer giving a more parti- 

 cular account of them, till the season for which they seem by nature to have 

 been designed. These eggs are of a regular oval figure, being about the 10th 

 part of an inch in length, and the 'iOth in breadth ; which, though it may seem 

 a very inconsiderable bulk, is certainly large for so minute an insect. When 

 they are first produced, their colour is green, but in a kw days turns to brown, 

 and by degrees becomes quite black. The covering of the eggs may be called 

 thick, if cotnpared with its small size, which at first is rather of a yielding na- 

 ture; but, after being exposed to the air, soon contracts a greater firmness. If 

 this covering is wounded, there issues forth a mucilaginous fluid, which is very 

 transparent, and in appearance of a uniform consistence. These eggs adhere 

 firmly to the branches on which they are deposited, by means of something glu- 

 tinous with which they are besmeared, and in a most surprising manner resist all 

 the severity of the winter. 



Though Dr. R. has just observed that the contents of the eggs have the ap- 

 pearance of a uniform fluid; that this cannot in reality be the case, sufficiently 

 appears from the aphides they produce in the spring, without any other aid tliaa 



