
No. 427.] HAIRS OF LEPIDOPTEROUS LARVE. 563 
was found to be especially useful; and, as the larger part of 
the work was based upon results thus obtained, it may be well 
to give the exact method of procedure. 
The fluid used for injecting was Griibler’s B.x methylen 
blue, į per cent solution in normal salt. The injection by means 
of a small syringe was made usu- 
ally in the side, back of one of 
the last abdominal segments, and 
enough liquid was injected to color 
the segments near the head, care 
being taken to insert the canula 
only under the hypodermis and 
muscles, and not into the alimen- 


42161 g eed dale 
IG. 3. — 8 
cornuta, showing large and small fla 
scales supplied with nerves and cells. tary canal. 
i gi 
e venas Au a After injection the animal was 
nerves demonstrated by methylen blue. left quiet for a period of about 
three hours for most insects, but with some, as with Pieris, 
two hours was a better time, and four hours seemed to be best 
for Datana larve. It is important that the insect remain 
preparation, the 
alive during this period after injection. 
When the proper period has elapsed the 
nerves and nerve cells should be well 
stained and almost all other tissues free 
from stain. After successful staining the 
specimen is cut open lengthwise and 
pinned out over a hole cut in sheet cork, 
the muscles and viscera are removed by 
careful dissection, and then, on examining 
under a microscope, the nerves and nerve 
cells are seen stained upon the surface 
of the unstained hypodermal layer. The 
bases of the hairs may be seen through 
the hypodermis, and it is easy to trace 
nerve cells and fibers in connection with them. By keeping 
the preparation wet with normal salt solution and using differ- 
ent powers of the microscope, much may be learned regarding 
the structure and distribution of the peripheral nervous system 
without further preparation; for this work the silkworm (Bombyx 

Fic. 4. — Section of hair 
of Datana. 
