CHEESE-MITES AND FLIES. 241 



honeycomb, sugar, and sweetmeats of various 

 kinds. A special mite is found in the cavities 

 of. the bones of skeletons ; indeed, there seems 

 scarcely any limit to this widely-spread family of 

 minute depredators. 



Other branches of the family are represented by 

 the Red Spider, which is one of the plagues of our 

 greenhouses, for, although so small as to be scarcely 

 discernible by the naked eye, it sucks the juices of 

 plants and often effectually prevents the healthy 

 growth of valuable specimens. 



The Plum-mite may frequently be seen in 

 clusters upon fruit-trees, puncturing the bark 

 and doing considerable injury to the smaller 

 twigs. 



A closely allied species is known as the Harvest- 

 bug. This almost invisible atom burrows into the 

 human skin and there deposits its eggs, causing 

 excessive irritation and annoyance to the workers 

 in corn-fields. 



I will now turn from the mites to another 

 cheese-inhabitant, Piophila casei. Few people are 

 likely to have noticed the perfect insect, a small 

 black fly with whitish wings margined with 



16 



