204 ARACHNOIDEA. 



CASE under the form of white dots, and sometimes contain a consider- 



XIV. 



able number of these Tyrogiyphi in the mterior of the body. 



The body of the large, especially the nocturnal Lepidoptera, the 

 Cicadse amongst the Hemiptera, the Earwigs, etc., etc., have 

 them likewise, and the quantity sometimes furnished by such 

 insects, wh-'^re the mites have once obtained a footing, is truly 

 enormous. 



The Tyroglyphus entomophagus may be found running upon 

 the back of dead insects, and may be seen without the aid of the 

 microscope. According to M. Ferris it gnaws the down and the 

 hairs of the insects attacked. It is, however, chiefly in the 

 inside of their body that it lives : it gnaws and dilacerates all 

 substances that are soft or deprived of chitine ; hence they are 

 specially destructive to Lepidopterous insects. In handling in- 

 sects that have been attacked by these Tyrogiyphi, we are apt 

 to cause the articulated pieces of which the ligaments have been 

 destroyed to fall asunder, and then there issues from the body a 

 friable matter in which the living Acari swarm. 



The friable matter which falls out, when the body of insects 

 gnawed by the Tyroglyphus entomophagus is shaken, is composed 

 (as shewn in the sketch in this case) : ist, of the excrement of these 

 animals in the form of little rounded greyish masses ; 2ndly, of 

 the eggs in course of development, and of empty shells of hatched 

 eggs, of open and bent shells, cracked often longitudinally ;.3rdly, 

 of young larvae and of nymphs always more numerous than the 

 adult animals ; 4thly, of tegumentary envelopes proceeding from 

 the moulting of a great number of larvae and nymphs ; 5thly, of 

 visceral or muscular remains of the body, of pieces of tracheae, of 

 striated muscular fasciae, of dried fragments, sometimes of eggs 

 which have not been laid, and which have become loose in the 

 body of the females of the attacked insects. 



In the dust at the bottom of the boxes, amongst the remains of 

 all kinds, antennas, feet, palpi, broken or fallen, one sometimes 

 finds the envelopes of Gamasus, of Glyciphagus and of Cheyletus, 



