FRUIT-TREES. 275 



111 different ftates of health, becaufe all do 

 not receive the infeftion alike. 1 muft own 

 I don't know how the fmother-flies are 

 bred s perhaps they may be in the fap of 

 the trees they are upon, but I rather ima- 

 gine from eggs or fpawn, firfl laid by in- 

 fers of the fame fpecies upon the furface 

 of ftagnant waters, v/hich bdng from 

 thence attrafted by the fun into the atmo- 

 fphere, and carried by the winds to differ 

 rent places, in the fliape and fubftance of 

 the honey-dews, and lighting upon fuch 

 branches or trees as are fuitable for its re- 

 ception, continues there till the infe6ls are 

 hatched and brought to maturity^ but a 

 great part of this matter falls upon bran- 

 ches or leaves of trees, where it feldom 

 hatches, as may be feen by its glittering 

 appearance on the leaves of the apricot, 

 and feveral other trees that are healthful, 

 which are more fmooth and compaft, when 

 young, than thofe of an unhealthful peach 

 and cherry, into which it penetrates -, as 

 alfo the plum, currant, goofeberry, and 

 many others. 



This pernicious matter is more injurious 



to the fore-mentioned trees (if weak or 



T 2 their 



