STRAW-COLOURED GNAT. 
preserve it for the microscope, this change may he retarded by 
keeping it in clear spring or river water. The former seldom offers 
sustenance to animalcules, and, therefore, effects this object, which 
is often very desirable, on account of the scarcity of this species.> 
The transformation of this animal from the larva to the pupa is 
one of the most singular and wonderful changes that can be con¬ 
ceived ; and, under the microscope, presents to the admirer of 
nature a most curious and interesting spectacle. Although the 
whole operation be under the immediate inspection of the observer, 
yet so complete is the change, that its former organisation can 
scarcely be recognised in its new state of existence. 
If we now compare the different parts of the larva with the. 
pupa, we remark a very striking change in the tail, which, in the 
previous state of being, was composed of twenty-two beautifully 
plumed branches, while, in the latter, it is converted into two 
fine membranous tissues, ramified with numerous vessels. This 
change appears the more remarkable, as not the slightest resem¬ 
blance can be discovered between them, nor are the vestiges of the 
former tail readily found in the water. The partial disappearance 
of the shell-like or reniform bodies is another curious circumstance. 
The lower two, it may be conjectured, go to form the new tail; 
for, if the number of joints be counted from the head, the new tail 
will be found appended to that joint which was nearest to them in 
the larva state, as referred to by the dotted line d, connecting 
figs. 1 and 2. The two small horns, c c , which form the white- 
plumed antennse of this species of gnat, when in its perfect state, 
are discernible in the larva, folded up under the skin near the 
head at c, in fig. 1. The alimentary canal appears nearly to 
vanish in the pupa, as in that state there is no necessity for it, 
the insect then entirely abstaining from food; while, near this 
canal, the two intertwined vessels, seen in the larva, have now 
become more distinct, and are supplied with several anastomosing, 
branches. 
During the latter part of the day on which the drawing (fig. 2) 
was taken, the rudiments of the legs of the perfect insect might 
be seen, folded within that part which appears to fie the head of 
the pupa, and several of the globules had vanished, those remaining 
longest that were situated near the head. It may be necessary to 
observe, that the head of the pupa floats just under the surface of 
the water; and the insect, in this state, is nearly upright in that 
fluid, while the larva swims with its body in a horizontal position, 
or rests on its belly or sides, at the bottom of the pond or vessel 
in which it is kept, the fringed tail being downwards. 
The colour of the larva when young is a faint and scarcely 
perceptible yellow ; but as it approaches the change, it assumes a 
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