among birds, the same louse often infesting n number of allied species, but among quadrupeds such a com 
munity of parasites is less frequent, The nuuibcr of different species is so large that as long a o 0 as 1H4_ 
Denny figured over two hundred belonging to mammalia and birds, without doing much mote than makin 0 
a preliminary survey of the subject. 
Still more limited is our present knowledge with regard to the parasites of insects; as to which, 
however, it is well known that many genera and species of the gamasiduc, a family ot the acarina or mites, 
live parasitically upon the bodies of other animals, and especially upon the bodies ol insects. Two examples 
are here offered selected from those species of the genus gamasus which occur parasitically upon beetles. 
No. 5. Gauiasus of the soldier-beetle magnified 45 diameters. Negative No. 505, new series. 
The prominent features of this mite, as shown in the photograph, are the oval body with eight hairy logs, 
each terminating in a small double hook; and the remarkable appendages of the head, viz the two long 
stout mandibles, terminating each in strong scissor-like extremities; externally to these are the curved 
five-jointed hairy palpi or feelers. 
No. fi. Appendages of the head of the same mite magnified 135 diameters. Negative No. 
506, new series. The photograph displays in detail the external configuration of the mandibles and palpi. 
One of the claws of the left hand mandible is broken. 
No. 7. Gamasus parasite on the burying-beetle ( Necroptiorus ) magnified 50 diameters. Negative 
No. 508, new series. This acarus is less hairy as well as smaller than that just described, its mandibles 
are shorter and their scissors-like extremities more crooked, but a great similarity exists between the two. 
No. 8. Anterior portion of the same gamasus magnified 135 diameters. Negative No. 509, new series. 
In this picture the appendages of the head can be more minutely studied. 
Not merely do the acarina furnish parasites for insects; many species exist upon the higher annuals. 
Some, like the Deiuodex follieulorum, which lives upon the human face, are quite innoxious; others, like 
the Sarcoptcs scabiei or itch insect of man, are the recognized causes of distressing skin diseases. 
No. 9. Acarus found by Bourgogne, of Paris, on the bat, magnified 80 diameters. Negative No. o02, 
new scries. The skin of this singular creature is beset with long hairs and each of the eight legs 
terminate in double hooks. 
No. 10. Parasite found by Bourgogne, of Paris, on a species of fly ( Volucella ) magnified SO diameters. 
Negative No. 522, new series. This parasite, which would appear to be, probably, some immature insect. 
I have been unable to identify. 
The foregoing examples of insect parasites might be multiplied indefinitely did time and leisure permit, 
and much more sihisfactory photographs could be produced if the specimens wore submitted to some pre- 
liininary bleaching process. 
I have the honor to be, General, 
Very respectfully, 
Your obedient servant, 
Assistant Surgeon , L. S. Army. 
