MICROSCOPIC DRAWING AND ENGRAVING. 
richer and deeper colouring, and all its internal parts acquire 
their definite forms and tints, as exhibited in the drawing. 
A curious circumstance attends the observation of this insect ; 
so rapid is its locomotion, that it torments the eye while attempting 
to delineate it, presenting alternately [its head and tail to the 
observer. This it effects by bending itself laterally into a circular 
form, and suddenly whisking round in the opposite direction to 
that in which it had just bent itself. 
Many species of this genus of insects are, in their perfect state, 
possessed of a sheathed proboscis, containing instruments with 
which they are enabled to pierce the skin of men and cattle, 
injecting at the same time an acrimonious fiuid into the wound. 
The species we are now describing, however, has not been 
examined minutely enough to determine the form of these organs. 
It is of a light straw colour, and has two beautiful antenna?, or 
feelers. 
The wings also of this gnat are of a delicate straw colour, and 
make very beautiful objects when mounted under thin glass in 
sliders. Some species have wings marginated, and covered with 
fine scales. These, as well as the feathers on the edges, are good 
objects for the microscope, and exhibit five or six longitudinal 
lines on each, which are so strongly marked as to be seen with 
any kind of light, and do not require superior penetration in the 
instrument to show them. 
These insects generate while hovering in the air, and the female 
lays her eggs in the water, selecting an unfrequented spot, where 
she may deposit them free from danger. This is probably the 
cause why this larva is discovered with so much difficulty; the 
collector being seldom able to procure it two seasons consecutively 
in the same place. 
59. The method of executing these drawings, practised by 
Dr. Goring, differed in nothing from that by which an artist 
makes a portrait, the eye guiding the pencil, and the accuracy of 
the resemblance depending altogether upon the skill of the artist. 
60. Dr. Goring considered that in such cases the great security 
for precision offered by the camera-lucida, was not available, 
owing to the constant mobility of the object delineated; this 
objection, however, is only applicable to living objects, and 
that admirable instrument is accordingly used to a great extent 
in the production of microscopic drawings. As we shall describe 
it in a future Tract, and explain its mode of application 
to the microscope, it will not be necessary here to give that 
exposition. It will be sufficient to observe that a practised 
draughtsman is capable of giving, not only the general outline, 
but most of the less minute details of a microscopic, object, by a 
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