APPENDIX C. — INSECTS. 379 



LETTER FROM T. R. PEALE, ESQ., UPON THE LARV^ OF INSECTS 

 FOUND IN THE GREAT SALT LAKE. 



Washington, May \2th, 1852. 



My Dear Sir : — The exuviae of insects which you have brought 

 from the shores of the Great Salt Lake proves, on examination, to 

 have 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 deter- 

 mine. 



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 accumu- 

 lated 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. 



