180 Dr. T. A. Chapman on 



one minute (60") ; to the completion of cutting, further 

 fifty seconds (50"). Then ten seconds (10") rest, and in 

 fifteen seconds (15") more, the egg was laid and the saw 

 withdrawn." 



On this occasion by giving attention to the point it was 

 clearly seen that the points of the saw curled round far 

 enough to cut a narrow portion behind the guide. 



I ought to have noted that in captivity at least it seemed 

 quite immaterial to the flies whether their heads when 

 laying were directed towards the tip or the base of the leaf, 

 nor did I notice that the legs were disposed in any constant 

 manner to secure a correct foothold. 



On May 1st the two Trichiosomas were getting rather 

 exhausted (they had probably been in existence some time 

 when captured). One could not be got to lay; the other 

 laid two eggs, but was rather stupid about it, as though her 

 instincts were failing. She kept getting too much on the 

 face of the leaf instead of on the edge, so that on three 

 attempts she failed to penetrate the leaf, the end of the saw 

 being too vertical to the face of the leaf and not in the same 

 plane with it, though I would not be positive that she did 

 not penetrate the cuticle but could then go no further. 

 On the two successful occasions, either from being out of 

 proper alignment or simply from exhaustion, after taking 

 about a usual time, 1' 20", to pierce, and 1' 0" to traverse, 

 she then rested in one case 3' 0" and in the other 4' 0" 

 instead of the usual 10" or 15", the actual laying and with- 

 drawing being as usual. Certainly the day was dull and 

 cool; for a successful observation a fairly warm day and 

 suitable fresh Salix were always necessary. 



The eggs were laid in leaves on cut branches in water, 

 so that their not increasing in size may be their usual habit, 

 or may have been the result of a want of a natural flow of 

 sap in the plant. The eggs I have had of several species 

 of sawflies have expanded in this way very notably. I 

 fancy, however, this species does not do so, as the egg duly 

 hatched in an apparently normal manner. On May 1st, 

 eggs laid on April 22nd had shown for several days the 

 outlines of the contained larva, as a denser circle within the 

 margin, but all very translucent and free from visible 

 structure except one small brown spot; at this date the 

 spot had got larger and more distinct, and had a rhythmical 

 to-and-fro movement, approaching and receding, by a 

 small distance, the end of the egg nearest the inlet to the 



