
THE SALMON DISEASE. LIS 22 

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Mr. Bolton, of Birmingham, in one of his portfolios of drawings, 
gives a photo-lithograph of a drawing illustrating Professor Rymer 
Jones’s paper on the structure and metamorphosis of the larva of 
Corethra plumicornis from the Quarterly Journal of Microscopical 
Science, 1867. 
Rev. J. G. Wood, in his “ Insects at Home,” page 608, gives a 
drawing of Zipula longicornis—one of the Craneflies—and_ along- 
side he depicts the larva and pupa, which I am disposed to think are 
incorrect, these being the larva and pupa of Corethra plumicornts. 
In Knight’s “Animated Nature,” page 360, the larva, pupa, and 
perfect insect are shown, the two former both magnified and 
natural size. The pupa is very active when disturbed, and rapidly 
finds the bottom of the aquarium. It gets rather darker as it ap- 
proaches its final change. After watching for some weeks in 
order to witness the imago emerge, I was enabled to do so on 
March 30, 
The pupa came to the surface and lay horizontally—being in a 
bottle it was easy to watch witha lens. After a few movements, 
it bent the body several times, until it split at the head, and the 
head of the imago rose out of the crack. It then disengaged first 
one foreleg and then the other, which were placed on the water, 
and after a short rest, the body was drawn out of its case, and the 
perfect fly was free. | 
The male Corethra is furnished with a pair of handsome plumes. 
The description of Corethra plumicornis in Walker's “ Insecta 
Britannica” is as follows :— 
‘Brown ; antennez testaceous, with brown bands; thorax with 
a whitish stripe on each side; pecters whitish; wings slightly 
greyish ; veins and borders thickly ciliated, the former testaceous ; 
halteres white ; abdomen pale brown, having legs pale, testaceous, 
pubescent. 
“* Male—Plumes of the antennz testaceous.” 

THE SALMON DISEASE.* 
OR some years past an epidemic disease has been known to 
prevail among the salmon in certain British rivers. The dis- 
ease has from time to time been attributed to various causes: the 
outward sign of its existence is the appearance of one or more 
whitish patches upon those parts of the body of the fish not covered 




* Abstract of ‘¢ A Contribution to the Pathology of the Epidemic known as 
the Salmon Disease.” A paper read at the Royal Society, March 2nd, 1882. 
By T. H. Huxley. 
