The Mason-bees 



mains packed in the slit and the furrow. The 

 delicate instrument thus almost completely en- 

 circles the abdomen. Underneath, on the 

 median line, we see a long, dark-brown scale, 

 pointed, keel-shaped, fixed by its base to the 

 first abdominal segment, with its sides pro- 

 longed into membranous wings which are fast- 

 ened tightly to the insect's flands. Its func- 

 tion is to protect the underlying region, a 

 soft-walled region in which the probe has its 

 source. It is a cuirass, a lid which protects 

 the delicate motor-machinery during periods 

 of inactivity but swings from back to front 

 and lifts when the implement has to be un- 

 sheathed and used. 



We will now remove this lid with the scis- 

 sors, so as to have the whole apparatus before 

 our eyes, and then raise the ovipositor with 

 the point of a needle. The part that runs 

 along the back comes loose without the slight- 

 est difliculty, but the part embedded in the 

 groove at the end of the abdomen offers a re- 

 sistance that warns us of a complication 

 which we did not notice at first. The tool, 

 in fact, consists of three pieces, a central piece, 

 or inoculating-filament, and two side-pieces, 

 which together constitute a scabbard. The 

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