48 Mr, W. BateBon on variation in the colour 



The paper and bag were bespattered with a brown juicy 

 substance, which will be described later. 



III. A number of apparently full-fed iarvfe were 

 similarly chosen and shut up in dark substances, and of 

 these six survived and spun as follows : — 



a. In black gauze, 1 specimen. Cocoon lighter than 



" half-colour." 

 h. On brown paper in green muslin bag, 2 specimens. 



Both quite white. 



c. On brown dried leaves in a green muslin bag, 2 spe- 



cimens. One white ; one very pale cream-colour. 



d. In the same bag of leaves as c ; spun on the green 



muslin, 1 specimen. Cocoon white. 



All these six cocoons, attached to dark substances, were 

 of light colour. There was a good deal of brown 

 evacuation, as in II. 



IV. Two larvfe, which had begun to spin in leaves, 

 were taken out and shut up in white paper. Both spun 

 cocoons of light colour. 



One larva, which had similarly begun to spin in a leaf, 

 was taken out, and it eventually spun a white cocoon 

 between green gauze and a piece of clear glass. 



One larva, beginning to spin on white paper, was 

 disturbed, and afterwards spun a white cocoon. 



Therefore, of 4 larvfe which were disturbed while spin- 

 ning, all spun light cocoons, 1 being on a dark substance, 

 3 being on white substances. 



These results leave little room for doubt that the 

 absence of colour in the cocoons results from an un- 

 natural condition, such as disturbance at the time of 

 spinning, or removal from food-plant when the growth 

 is nearly complete. Besides these the presence of para- 

 sites should be mentioned as sometimes associated with 

 a similar effect. This was seen once in a specimen of 

 E. lanestris, and once in ^S. crtr_/jr/a', which were inhabited 

 by a Tachina. In both these cases the cocoons were 

 quite white. On the other hand, several Tachina were 

 found in one Saturnia cocoon of dark colour. It will be 

 seen, therefore, that though these observations fully 

 confirm the statement that the larvre do spin dark 

 cocoons on the leaves, and white cocoons when confined 

 in white paper, yet they suggest that the operating 

 cause is the confinement and not the whiteness of the 



