20 Dr. John Davy's Observations on 



when evaporated and heated, a shght but distinct trace, in the 

 color produced, of hthic acid. 



These few are all the trials I have to notice on the excrements 

 of larvae. With the exception of the last, in this country, they 

 were all made in Barbados. 



The next I have to mention were on the excrement of the per- 

 fect insect, immediately after quitting its puparium; these likewise 

 were made in Barbados. 



7. The pupa of the caterpillar,- number 1, I may premise, occurs 

 attached by a fine, short thread and hanging perpendicularly. 

 Before the escape of the imago the color of the chrysalis changes 

 from apple green to a dull blue, passing into brown; becoming 

 when empty of a light grey. On quitting its case the butterfly 

 adheres to it, its head upwards, its wings hanging down. Thus it 

 remains motionless, with the exception of occasionally expanding 

 its wings, till the intestine has been unloaded, fitting it for flight, 

 secure from its position of not being soiled in the slightest degree 

 by what it voids. The discharged matter I have found to vary 

 in different instances, and this at the same season, and when 

 voided by individuals similarly reared, and detached from the 

 same shrub. The excrement of one was a turbid liquid of a 

 purplish hue, as if tinged by the purpurate of ammonia. Under 

 the microscojje, there were to be seen purple patches, some color- 

 less rhomboidal plates, as if of lithic acid, and numerous granules, 

 as of lithate of ammonia. By the test of nitric acid and heat, 

 manifest proof was obtained of the presence of lithic acid, a 

 strong purple color being produced. The excrement of another 

 was of a brownish hue, and turbid. In it were detected traces 

 of hippuric acid, of lithic acid, and of urea, judging from the 

 form of the crystals obtained from an alcoholic solution, from 

 the effect of nitric acid, and of that of this acid and of heat. 

 The excrement of a third, also a brownish fluid, appeared to 

 contain little else than hippuric acid, with perhaps a trace of urea. 

 The extract obtained from the alcoholic solution of the dried 

 matter emitted, on the addition of nitric acid, an odour like that 

 of the urine of the horse, and afforded crystals on evaporation 

 similar to those from the same urine when treated in like manner. 



8. A Sphinx from the larva number 4, on quitting its pupa- 

 rium voided a considerable quantity of brownish turbid fluid. 

 This excrement afforded distinct traces of lithic acid in the form 

 of lithate of ammonia, and also of hippuric acid ; the former in 

 suspended granules, the latter in solution. The lithic acid was 

 indicated by the effect of nitric acid and heat; the hippuric acid 



