158 HISTORY OF 



are fond of honey-suckles, lilac, and wild-cherry 

 shrubs ; but some that have sought after them 

 declare, they never could find them on elder trees, 

 nut trees, and among wheat. We are told that 

 the country people expect the return of these 

 insects every seven years. It is very certain 

 that such a number of these insects have been 

 seen together in the air, that they appeared like 

 swarms of bees ; and that they have so disagree- 

 able a smell, that it may be perceived a great way 

 off, especially about sun-set, though they are not 

 seen / at that time. This bad smell is a guide for 

 those who make it their business to catch them. 

 When they are caught, they dry them, after 

 which they are so light, that fifty will hardly 

 weigh a drachm. Those that gather them, tie 

 them in a bag, or a piece of linen cloth that has 

 been well worn, and then they kill them with 

 the vapours of hot vinegar, after which they dry 

 them in the sun, and keep them in boxes. These 

 flies, thus dried, being chemically analyzed, yield 

 a great deal of volatile caustic salt, mixed with a 

 little oil, phlegm, and earth. Cantharides are 

 penetrating, corrosive, and, applied to the skin, 

 raise blisters, from whence proceeds a great 

 deal of serosity. They are made use of both in- 

 wardly and outwardly. However, it is somewhat 

 strange that the effects of these flies should fall 

 principally upon the urinary passages ; for though 

 some authors have endeavoured to account for 

 this, we are still in the dark, for all they have 

 said amounts to no more, than that they affect 

 these parts in a manner which may be very 



