Urinary Excrement of Insects, 337 



yield purpurate of ammonia, I had the curiosity to weigh. 

 Using a balance of great delicacy, I found it to weigh -008 

 grain ; that is, under one-hundredth part of a grain ! 



Moths. — I have examined the excrement of at least three 

 different species of night moth ; one white, one yellow, and 

 one brown. In each instance lithic acid was comparatively 

 abundant, especially in that of the brown. The excrement 

 of this moth was very copious for its size, of a reddish hue 

 and soft consistence. Under the microscope, it appeared to 

 consist chiefly of granules, and of rhomboidal plates, with 

 which were mixed two or three hexahedral plates. One 

 moth weighed 16 grain ; more lithic acid was found in its 

 urinary secretion than in that of a humming-bird, the weight 

 of which was 92-5 grains, and which I find subsists chiefly on 

 minute insects. The granules composing the granular mat- 

 ter of the excrement of these insects, probably lithate of am- 

 monia, were commonly about g oVo of an inch in diameter. 



Butterfly, — A large butterfly of a mixed purple and brown 

 colour with white spots, fed whilst confined on syrup, yielded 

 some liquid excrement of a light-brownish hue, which, care- 

 fully tested by nitric acid, afforded indications both of urea 

 and of lithic acid. The first were obtained by evaporating it 

 with a very minute quantity of nitric acid, when crystals 

 similar to those of nitrate of urea were visible under the 

 microscope. The latter were obtained by heating the acid 

 solution of the excrement, when the characteristic tint of 

 purpurate of ammonia appeared ; but it was faint, proving 

 that the proportion of lithic acid present was exceedingly 

 small. 



Mantis. — A large species of this insect, in confinement, 

 voided a good deal of excrement ; some blackish, faecal ; 

 some in little brownish masses, and probably chiefly urinary. 

 The latter, under the microscope, appeared to consist chiefly 

 of globular particles, of nearly sAu i^^ch in diameter, and 

 which, it may be inferred, were composed chiefly of lithic acid, 

 from the purpurate of ammonia produced by the action of 

 nitric acid heated with the excrement. 



Spiders. — In the more recent zoological arrangements, 

 spiders have been removed from the class of insects. Their 



