236 DISEASES OF INSECTS. 



fixed : when hatched or released for perhaps they may 

 be regarded as foetuses in their amnios rather than eggs 

 they cease to be parasitical. Let us admire on this 

 occasion, (piously observes this great Entomologist,) the 

 different and infinitely varied means by which the AU- 

 THOR of Nature has endowed animals, particularly in- 

 sects, for their propagation and preservation : for it is a 

 most extraordinary sight to see eggs grow, and pump as 

 it were their nutriment from the body of another living 

 animal a . As these mites are fixed to the crust as well as 

 its inosculations, they must have some means of forcing 

 their nutriment through its pores. 



Another insect, remarkable for its resemblance in some 

 respects to the scorpion called in this country the book- 

 crab (Cheli/er cancroides], from its being sometimes found 

 in books occasionally is parasitic upon flies, especially 

 the common blue-bottle-fly (Musca vomitoria). They 

 adhere to it very pertinaciously under the wings ; and if 

 you attempt to disturb them, they run backwards, for- 

 wards, or sideways, with equal facility. 



Spiders also are infested by mites. Mr. Briggs once 

 found a very small Theridion^ to the thorax of which 

 were attached four oblong bright scarlet mites, each of 

 which was as large as the thorax itself. He afterwards 

 met with another spider still smaller, attacked by two of 

 these swoln parasites, one of which appeared to him 

 nearly equal to the spider in size. This mite was pro- 

 bably either Leptus Phalangii, or Astoma parasiticum. 



2. We now come to a perfectly distinct tribe of in- 

 sect parasites, which belong to that section or order of 



a De Geer vii. 144. 



