photographs of some of the external 
Letter to the Surgeon General of the Army accompanying seven 
appearances of the Mosquito. 
Army Medical Museum, 
January 5, 1872. 
BRIGADIER GENERAL J. Iv. BARNES, 
Surgeon General. U. S. Army. 
General: During the recent Christmas holidays I employed a few mornings in making photographs 
of the microscopical appearances of certain insect preparations. It was my desire to comply with the wish 
you had not long before expressed that I would put into your hands a few representations of familiar 
objects which might serve to illustrate, to intelligent persons unacquainted with the technical details of 
histological research, the powers of the microscope and the possibility of fair photographical illustrations 
of microscopical subjects. 
The series of negatives produced represent: 1. The external appearance of the Mosquito. 2. Certain 
Parasites. 3. The Proboscides of various Flies. 4 Some miscellaneous views of insects and parts of insects. 
In submitting these pictures for your favorable consideration, 1 beg you to understand that I do not 
offer them as scientific studies of the objects represented The microscopical work conducted under my 
supervision at the Museum is necessarily confined to the investigation of disease, and so much of uorrnal 
histology as is indispensable to the right comprehension of morbid processes. The present effort is there- 
fore quite out of my usual line of work and the result must be judged with a full understanding of that 
fact. To make a sincere scientific investigation of the anatomy of the Mosquito alone, to prepare the 
necessary specimens and to reproduce them photographically, would be at least an undisturbed year’s hard 
work for the most zealous microseopist. Such an investigator, had he fortunately the time and means at 
his disposal, w-ould so modify his specimens by the use of proper bleaching and other reagents, as to render 
it possible to photograph the least detail in the most satisfactory manner; whereas I, compelled from the 
circumstances of the case to make use of such ready made specimens as I could procure in the market at 
a nominal cost, could only hope in the brief time at my disposal to indicate what might have been done in 
the same direction under more favorable circumstances. 
With these preliminary remarks I proceed to a brief description of the series representing the external 
appearances of the Mosquito. 
These photographs represent views of different portions of a male Mosquito prepared by Mr. W. II. 
Walmsley of Philadelphia. Pa. 
The Mosquito of the United States is closely allied to the Gnat of Europe which has been so often 
the subject of microscopical writers 
The first photograph (Negative No. 493, new series) gives a view of the whole insect magnified eleven 
diameters by Beck’s 4 inch objective. Even with this low power the plumose antennae, the complex 
stinging and sucking apparatus, the six legs, the abdominal segments, and the terminal hooks of the tail 
are plainly indicated. The plumose antennre and the hooks of the tail arc peculiar to the male insect, the 
same parts being quite different in the female. 
The second photograph (Negative No. 495, uew series) represents the head of the Mosquito magnified 
90 diameters by Beck’s 2-3rds. 1 A portion of the hexagonal facets of the compound eyes are indicated, and 
portions of the branching auteunse and other appendages of the head with their hairs and scales are shown. 
