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Some additional Observations on the Urinary Excrement of In- 

 sects. By John Davy, M.D., F.R.S., Lond. & Ed., Inspec- 

 tor-General of Army Hospitals. Communicated by the 

 Author. 



In a former communication, I noticed the results of experi- 

 ments tending to prove that the urinary excrement of many 

 different species of insects in their perfect state— all that I 

 examined— consisted chiefly of lithate of ammonia. Since 

 then I have subjected to trial the excrements of caterpillars, 

 of two or three kinds of butterflies, and also of hawk-moths 

 and likewise the excrement accumulated in the larva state of 

 each, and voided by them immediately after quitting the pu- 

 parium, on assuming the imago form, and preparatory to 

 taking wing and exercising the functions of the perfect in- 

 sects. 



The excrement of caterpillars, obtained when feeding on 

 leaves, was chiefly fa^cal and very abundant, voided in small 

 dark cylindrical masses. Acted on by very dilute nitric acid, 

 and by alcohol, using separate portions, a very little lithic 

 acid was detected in it, which probably existed as lithate of 

 ammonia in the excretion, and some hippuric acid, judgino- 

 from the crystals found on evaporation after solution in mu- 

 riatic acid, and from other properties. 



The excrement of the caterpillars of the hawk-moths, when 

 feeding, was very similar in appearance to the preceding, and 

 resembled it also in composition. Hippuric acid was detected 

 in it and lithic acid, and the latter in larger proportion, in- 

 deed, in one instance, it was to be seen adhering to the little 

 excrementitious masses as a whitish incrustation. This under 

 the microscope was found to consist of globules of about 

 Tijooo of an inch in diameter; and it had the properties of 

 lithate of ammonia. 



The excrement voided by the butterflies I have had under 

 observation immediately after quitting their puparia, has • 

 commonly been a brownish turbid fluid. I have detected in 

 it a very little lithate of ammonia, and u considerable pro- 

 portion of hippuric acid. In one instance that the fluid had 

 VOL. XLV. NO. LXXXIX.— .JULY 1848. B 



