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Show APPENDIX C.- INSECTS. 879 LETTER FROM T. R. PEALE, ESQ., UPON THE LAKVM OP INSECTS FOUND IN THE GREAT SALT LAKE. WASHINGTON, May 12ft, 1852. * MY DEAR SIB:- The exuviae of insects which you have brought from the shores of the Great Salt Lake proves, on examination, to bave been deposited by aquatic diptera. In the mass, I can detect fragments of the larvae shells of the pupa, and small portions of a mature Chironomus and other Tipulidae. More than nine- tenths of the mass is composed of larvae and exuviae of Chironomus, or some species of mosquito- probably undescribed; the fragments being too imperfect to determine. You are best able to determine, first, whether mosquitoes exist at any time at the Great Salt Lake in such unparalleled numbers as this organic matter indicates; or, secondly, whether the salt of the lake water has preserved their exuviae, so that it has accumulated through a great length of time. A few fragments of insects I have been able to determine as belonging to the Linnaean genus Nepa> which is aquatic, and a very few others as Hymenopterous, & c. In the hope of soon seeing your Report on the most interesting portion of our continent, I remain Yours truly, T. R. PEALE. CAPTAIN H. STANSBURY, Corps Topographical Engineers, Washington. I am not aware that mosquitoes exist in such unusual abundance in the vicinity of the lake; but incline to the opinion of Mr. Peale, that the accumulation of the immense masses of these exuviae is to be attributed to the preservative qualities of the lake water. H. S. |