6 DR. BRACKENRIDGE CLEMENS' LETTERS. 



from the cocoon, except in this one instance. I copy from 

 my note-book as it was recorded at the time of observation. 



" My attention was first attracted by a crackling and movc- 

 " ment within the cocoon, and after attentively observing it, 

 " I perceived its inmate had already engaged itself in the 

 " work of delivery and was producing a dilatation of the 

 " tapering portion, where the threads are left thin and con- 

 " vergent to the larva. In a short time I could perceive a 

 " dark outline dimly shown through the lax structure of the 

 " apex, and could notice more clearly the dilating effort made 

 " by the imago, and that it was confined principally to two 

 " points of the circumference of the cocoon. After making 

 " an effort of a few seconds' duration to advance itself, the 

 '* imago rested for the purpose of recovering from its fatigue, 

 " and also, as I afterwards ascertained, of moistening the 

 " structure with a colourless secretion, which exudes from 

 " the mouth and dissolves the gummy substance by which 

 " the threads of the cocoon are agglutinated. 



" Presently the head, eyes and anterior portion of the 

 " mesothorax were protruded from the apex and were clearly 

 " visible, though still covered with many unruptured threads, 

 " and the insect rested in this position for a moment. When 

 " the extruding efforts were recommenced, I could distinctly 

 " see that the dilating and extruding impulse was produced 

 " by an outward and backward movement of the Aving-shoul- 

 " ders, the motion of which Avas as distinct and evident as 

 " that of one's elbows would be were the human body simi- 

 " larly confined. 



" When the thorax was finally protruded the feet were 

 " folded upon it and appeared not to have been used as aids 

 " in any manner. Indeed, the pressure of the cocoon around 

 " the confined portion of the body was apparently too great 

 " to admit of any movement of the legs. After the liberation 

 " of the feet, the insect used them as aids in the extraction 

 " of the abdomen, which was very large, the specimen being 

 " a fine female. But the chief means by which abdominal 

 " delivery was effected, was a curious vermicular movement, 



