XXI EXPERIMENTS 291 



does not suggest an obstacle to it. Beyond, it sees a 

 frees pace bathed in sunshine. It exhausts itself in 

 efforts to fly there, unable to comprehend the useless- 

 ness of struggling against this strange, invisible 

 barrier, and perishes, obstinate and exhausted, with- 

 out a glance at the gauze which closes the conical 

 tube. The experiment must be repeated under 

 better conditions. 



The obstacle I selected was common gray paper 

 — opaque enough to keep the insect in the dark — 

 thin enough not to offer serious resistance to the 

 prisoner's efforts. As there is a vast difference by 

 way of obstacle between a paper partition and a 

 vault of unbaked clay, let us see first if Chalico- 

 doma muraria knows how, or rather if it is able, to 

 pierce such a barrier. The two mandibles — pickaxes 

 adapted to pierce hard mortar — are they also scissors 

 capable of cutting thin material ? That is the point 

 to be ascertained. 



In February, when the insect is already in the 

 perfect state, I withdrew a certain number of 

 cocoons uninjured from their cells, and placed each 

 separately in a piece of reed, closed at one end 

 naturally, open at the other. The pieces of reed 

 represented the nest-cells. The cocoons were intro- 

 duced so that the head of the insect should turn to 

 the opening Finally, my artificial cells were closed 

 in various ways. Some had a stopper of kneaded 

 earth, which, when dry, answered in thickness and 

 consistency to the mortar of the nest ; others were 

 shut by a cylinder of Sorghum vulgare at least a 

 centimetre thick, and others with a stopper of gray 

 paper, solidly fixed by its edges. All these bits of 



