CHEESE-MITES AND FLIES. 243 



emitting a liquid which softens and corrupts the 

 cheese and renders it suitable for the food of the 

 maggot. 



The leaping power of these larvae is truly sur- 

 prising. Swammerdam, who seems to have carefully 

 studied this creature, says: " I have seen one whose 

 length did not exceed a fourth of an inch leap out 

 of a box six inches deep, that is twenty-four times 

 the length of its own body." The grub cannot 

 crawl, as it has no legs ; it must therefore progress 

 by leaps ; this it achieves by erecting itself on its 

 tail, which is furnished with several knobs or warts 

 to enable it to keep its balance ; then, bending itself 

 into a ring, it lays hold of the skin of its tail, and, 

 suddenly letting go with a jerk, it can, by a succes- 

 sion of springs, cover a surprising distance on a 

 level surface. In considering the life-history of 

 this despised creature I cannot but endorse the 

 devout remark of the great naturalist I have just 

 quoted. He says : " I can take upon me to affirm 

 that the parts of this maggot are contrived with 

 so much art and design that is impossible not to 

 acknowledge them to be the work of infinite power 

 and wisdom from which nothing is hid and to 



