122 



ANIMAL PARASITES AND MESSMATES. 



feathers with astonishing facility, and it is not always 

 confined to the same bird; it quits its host to establish 



Fig. 14.— Flesh Fly. 



Fig. 15.— House Fly. 



itself upon another, and sometimes throws itself upon 

 man to suck his blood. 



Some years ago these insects penetrated in the 

 middle of the night through the open windows into one 

 of the apartments of the military hospital at Louvain, 

 and the next morning the skin of many of the patients, 

 and especially the bed-linen, were covered with stains of 

 blood. The physicians sent me some' of these insects, 

 not knowing whence they had come, nor whether they 

 had been the cause of this annoyance. During the 

 night, these Ornithomyse had quitted their hosts to 

 attack the soldiers. 



One of these insects, the banded Syrphus (Syrphus 

 balteatus), when in the larva, state, seizes the rose 

 aphides, and sucks their blood with great eagerness. 



But it is not precisely a case of parasitism, when 

 the wounds of soldiers are covered with larvae, of which 

 there were many sad instances in the Crimean war. 

 There are flies which deposit their eggs in pus, as in 



