The Mason-bees 



been able to discover. What about a dissol- 

 ving-fluid which would soften the mortar un- 

 der the point of the ovipositor? No, for I 

 see not a trace of humidity around the point 

 where the thread is at work. I fall back 

 upon a fissure, a lack of continuity somewhere, 

 although my examination fails to discover any 

 on the Mason-bee's nest. I was better served 

 in another case. Leucopsis dorsigera, Fab., 

 settles her eggs on the larva of the Diadem 

 Anthidium, who sometimes makes her nest In 

 reed-stumps. I have repeatedly seen her In- 

 serting her auger through a slight rupture in 

 the channel. As the wall was different, wood 

 in the latter case and mortar In the former, 

 perhaps It will be best to look upon the mat- 

 ter as a mystery. 



My sedulous attendance, during the best 

 part of July, In front of the tiles hanging 

 from the walls of the arch, allowed me to 

 reckon the inoculations. Each time that the 

 insect, on finishing the operation, removed Its 

 probe, I marked In pencil the exact point at 

 which the instrument was withdrawn; and I 

 wrote down the date beside it. This Inform- 

 ation was to be utilized when the Leucospis 

 finished her labours. 



294 



