Dr Davy on the Urinaria Excrement of Insects. 335 



The development of these, and a practical mode of their 

 application, I have exhibited before you, and shall be ready 

 to prove their accuracy, and the practicability of my mode of 

 applying them, on any other occasion that may present itself. 



Additional Notice on the Urinary Excrement of Insects, with 

 so?ne Observations on that of Spiders. By JoiiN Davit, 

 M.D., F.R.S.L. & E., Inspector- General of Army Hospi- 

 tals. Communicated by the Author. 



In the present number of this Journal, at page 231, a notice 

 was inserted, containing the results of an examination of the 

 urinary excrement of a small number of insects. Since the 

 date of that notice I have been able to extend the inquiry, 

 and I now propose to communicate the additional facts I 

 have ascertained, with an account of some experiments on 

 the same excretion from spiders. 



Field-Cricket. — An insect of this kind, confined under glass 

 and fed on bread, voided a good deal of excrementitious mat- 

 ter, in small oval masses of a light-brown colour and soft 

 consistence, having a urinous smell. It appeared to be 

 partly faecal and partly urinary ; for under the microscope 

 scales were detected in it and grains, which were found to 

 be of starch by the test of iodine ; and also lithic acid by 

 the test of nitric acid aided by heat. The lithic acid was 

 minute in quantity. I suspected urea likewise might have 

 been present, but I could not detect it. 



Beetle. — One similar to that of a former trial, resembling 

 the Scarabasus pilularius, yielded, in confinement, a large 

 quantity of excrement, which was found to consist chiefly of 

 lithic acid, and it may be inferred in the form of lithate of 

 ammonia ; for, besides giving a rich purple tint when heated 

 with nitric acid, it was soluble in water like lithate of am- 

 monia. 



In the excrement of another insect of the coleopterous 

 kind, small, of elegant form, with cushion-feet, lithic acid 

 was detected distinctly, but with difficulty ; it appeared to 

 encrust the faecal masses. 



Mason Bee. — One in confinement, yielded a little excre- 

 ment, which was semitransparent and of a brownish hue. 



