638 



THE MICROSCOPE. 



norum is found on dried plums, &c. ; Ac. favor um finds 

 its food in old honeycombs ; Acarus sacchari (fig. 291) is 

 commonly present in the more impure kinds of sugar. 

 The discovery of the general prevalence of this acarus 

 rests, we believe, with Dr. Hassall. 



The Sugar acarus approaches somewhat, in its organisa- 

 tion and habits, Acarus domesticus ; it attains to a size so 

 considerable, that it is plainly visible to the unaided sight. 



Fig. 291. 

 Ova and young of the Acarus sacchari, Sugar-Insect, after Hassall. 



When present in sugar, it may always be detected by the 

 following proceeding : two or three drachms or teaspoonfuls 

 of sugar should be dissolved in a large wine-glass of tepid 

 water, and the solution allowed to remain at rest for an 

 hour or so ; at the end of that time the acari will be 

 found, some on the surface of the liquid, some adhering to 

 the sides of the glass, and others at the bottom, mixed up 

 with the copious and dark sediment, formed of fragments 

 of cane, woody fibre, grit, dirt, and starch-granules, which 

 usually subside on the solution of even a small quantity of 

 sugar in hot water. The Acarus sacchari, when first 

 hatched, is scarcely visible ; as it grows it becomes elon- 

 gated and cylindrical, until it is about twice as long as 



