\*^ fJanuarv. 



any mure. All these eggs produce males ; the conclusion is that the 

 female now wishes to pair, and will thereafter lay eggs producing 

 females ; but one wants observation in addition to inference, and so far 

 I have not succeeded in getting any jDairings in these saw-flies 



On May 10th, 1917, already a large number (all males) of Trichio- 

 soma tihlale (hawthorn) had emerged from the cocoons afforded by 

 larvae reared last summer. 



The process of emergence from the cocoon was observed in a number 

 of instances. To find an emerging fly, one listens to the jar containing 

 the cocoons, and, if one is emerging, the crackle of the jaws of the fly on 

 the cocoon is heard, and a search soon finds the cocoon involved. If all 

 goes well, the whole process does not take many minutes. 



The cutting off of the lid is, of course, done b}'^ the jaws, but not in 

 the way one presupposes ; the first thing to attract one's attention is that 

 the slit is freely bathed b}' some liquid, sometimes plentiful enough to 

 wet some of the outer surface of the cocoon and always to wet a good 

 deal of the head of the fly, probably inevitable, as in the revolution of 

 the fly in cutting the whole circle, the back and other portions of the head 

 touch the surface already cut on the side opposite to that being cut at 

 the time. The next point is that the jaws do not act by gnawing, as 

 one might, indeed, have concluded from their structure, being sharp- 

 pointed and not constructed for gnawing ; the lid is also evidently cut 

 off. But it is not cut by a scissors-action of the jaws, as would seem to be 

 a very probable method of action from the pointed ends and sharp inner 

 ejges. 



The actual process is that the point of one jaw is thrust through the 

 cocoon (softened by the fluid ?) up to the first of the two teeth on the inner 

 edge, the point of the other jaw engages the inner surface of the cocoon 

 several millimetres back and at a point towards which the cutting-jaw 

 is drawn, and in being so drawn the cocoon is cut in the required direc- 

 tion b}^ the sharp edge, just beyond the teeth and apparently also by the 

 edge of the first (and at times, second?) tooth, the line of cocoon to be 

 cut falling into the angle between the tooth and the forward inner 

 cutting-margin of the jaw. The incision is thus made by one jaw only, 

 in much the same way as paper or cloth is sometimes cut by a pair of 

 scissors, when they are not used as scissors, but the two blades remaining 

 unmoved as regards each other, the paper is cut at the angle between 

 them, or really by the edges of the two blades where they meet, but by 

 a knife, not a scissors, action — a futile procedure unless the paper is 

 firmly held, as the cocoon is by the other jaw. A certain poi-tion being 



