the Excrement of Insects. 27 



water. A single musquitoe weighed was found equal to about 

 •008 of a grain. The balance used was a delicate one, of Robin- 

 son's construction. 



35. A large fly (four white bars on its thorax, white spots on 

 abdomen, yellow about the eyes), in confinement, voided some ex- 

 crement, partly in small cylindrical masses of a fawn color, partly 

 spread out and semifluid, of a light brownish hue. In the former, 

 under the microscope, two forms of crystals were seen ; one like 

 those of lithic acid ; the other like those of ammoniaco-magnesian 

 phosphate. In the latter, granules only were seen. Both acted 

 on by nitric acid and heat, afforded proof of the presence of lithic 

 acid. 



^Q, A mason-bee, in confinement, voided a very minute portion 

 of excrement, semi-transparent, semifluid, and of a brownish 

 hue. By the usual test, it was found to contain lithic acid. 



37. An elegant beetle with cushioned feet, in confinement, 

 voided several small pellets, some of them with a brownish incrus- 

 tation. These, the incrusted ones, acted on by nitric acid and 

 heat, afforded distinct traces of lithic acid. Examined under the 

 microscope, they appeared to be composed principally of vege- 

 table matter. In those without incrustation, and of a darker hue, 

 no lithic acid could be detected ; they were, probably, entirely 

 faecal. 



38. A brown speckled moth, its wings spotted white, in con- 

 finement voided a comparatively large quantity of brownish ex- 

 crement of soft consistence. Under the microscope, fine granular 

 matter — the granules about -g-jj^^ of 'Hi i"ch in diameter — were 

 observable, and many crystals ; of these, some were reddish 

 brown, some colorless ; some, the majority, were rhomboidal plates 

 of moderate thickness ; others nearly cubical ; one plate, a color- 

 less one, was hexagonal. They varied in size ; they were large 

 microscopical objects as seen with an Ath inch glass. A drop of 

 nitric acid added, the granules were instantly dissolved, the 

 crystals slowly. The solution evaporated and heated, acquired a 

 rich purple hue. The granules, it may be inferred, were of lithate 

 of ammonia; the crystals, probably, in most part, of lithic acid. 



Ail these observations on perfect insects, with one exception, 

 were made in Barbados ; the single exception was that on the 

 fire beetle, which was made in Trinidad. The observations which 

 I am now about to offer were made in this country, and the 

 greater number of them in the neighbourhood of Ambleside. In 

 recording these latter results, I have had the advantage in most 

 instances of beincr able to assign correct names to the insects, tlieir 



