DIUECT BENEFITS FROM MOTHS. 71 



circulation. Another important distinction between 

 these caterpillars and vertebrate animals is, that 

 they have no brain ; their nervous system consist- 

 ing of ganglions, or the nervous filaments united at 

 intervals, by little knobs. Neither have they 

 lungs, and they breathe by means of small spiracles, 

 or air holes, placed in the middle of the segments, 

 or rings, of the caterpillar, on each side ; these 

 again communicate, and end in the throat by means 

 of tubes. The spinning apparatus is situated near 

 tlie mouth, and connected by means of long slender 

 vessels with the silk bags. 



The external tube by which the silk is produced, 

 has been termed the spinneret, which Reaumur 

 supposes to have two orifices for the extrusion of 

 the silk, which, however, the accurate Lyonnet 

 found to unite before their reaching the termination 

 of the tube ; and discovered that it was composed 

 of alternate slips of horny and membranaceous sub- 

 stance, — the one intended for compressing the fila- 

 ment into small diameter, and the other for enlar- 

 ging it at the will of the animal. Its point is tnm- 

 cated like the nib of a pen, which admirably adapts 

 it for applying it to any object. Lyonnet has 

 given full and satisfactory delineations of dissec- 

 tions of all the silk-spinning apparatus of motlis. 

 The species he selected for this purpose was the 

 caterpillar of the Goat Moth, P. cossus. 



