the Excrement of Insects. 19 



cylindrical masses of a dark olive green, some of wliich were par- 

 tially covered with a yellowish crust. The matter of this incrus- 

 tation was found to be chiefly lithate of ammonia. Under the 

 microscope it was seen to consist of spherical granules, most of 

 them about ^oQYjfj of an inch in diameter; these were dissolved 

 immediately in dilute nitric acid, and when heated (a drop of the 

 solution being placed on a slip of thin glass), acquired the rich 

 purple hue characteristic of lithic acid under this treatment. 



3. A large caterpillar of a Sph'mx, after it had ceased feeding, 

 about to assume the chrysalis state, put under a glass cover, in 

 less than twenty-four hours parted with its enveloping integu- 

 ments, and became completely incased ; in doing so, it voided a 

 good deal of brownish fluid. This, tested for lithic and hippuric 

 acid, afforded no traces of the former, but pretty distinct ones of 

 the latter. 



4. Another large caterpillar of a Sp/iinx, in a state very similar 

 to that of the preceding, was very restless in confinement, and 

 shortly voided some dark fluid excrement, which, on examina- 

 tion, gave results like those last mentioned. 



This caterpillar was killed by immersion in spirits of wine. 

 Opened, its stomach was found to be the most conspicuous organ ; 

 it extended nearly the whole length of the abdominal cavity, and 

 was distended with a dark, mucous fluid. Under the microscope 

 a tubular structure was seen contiguous to it, and connected with 

 it. Conjecturing that these tubes might be renal ones, the part 

 was taken out, and digested in water, to which a little nitric acid 

 had been added : the solution formed was found to contain lithic 

 acid; thus a drop of it evaporated, and heated on a support of 

 thin glass, acquired the rich purple tint distinctive of this acid. 



5. A large caterpillar of another species of Sphinx, taken from 

 the leaves of the sweet potatoe on which it was feeding voraci- 

 ously (in confinement still feeding), voided a great deal of almost 

 black excrement, in cylindrical masses, rounded at their ends. 

 On none of them was there any appearance of incrusting matter, 

 as in the instance No. 2. They yielded a brownish solution to 

 proof spirit; and this evaporated, afforded an extract, which, 

 with nitric and muriatic acid, afforded crystals, some of them of 

 the form of hippuric acid similarly combined. 



6. A silk worm actively feeding on mulberry leaves voided ex- 

 crement in the form of small black pellets : on one of them there was 

 a brown incrustation; this, agitated with a drop of water, rendered 

 the water slightly turbid. Under the microscope it exhibited 

 granules; these were soluble in dilute nitric acid, and afforded, 



c 2 



