588 INSECT ARCHITECTURE. 



when nearly finished, a large stone is added by way 

 ■of ballast. In other instances, when the materials 

 are found to possess too great specific gravity, a bit 

 of light wood, or a hollow straw, is added to buoy 

 up the case. 



Nest of Caddis-ieorm balanced ^nth Straw/;. 



It is worthy of remark, that the cement, used 

 in all these cases, is superior to pozzolana* in stand- 

 ing water, in which it is indissoluble. The grubs 

 themselves are also admirably adapted for their 

 mode of hfe, the portion of their bodies which is always 

 enclosed in the case, being soft like a meal-worm, or 

 garden caterpillar, while the head and shoulders, 

 which are for the most part projected beyond the 

 door-way in search of food, are firm, hard, and con- 

 sequently less liable to injury than the protected por- 

 tion, should it chance to be exposed. 



We have repeatedly tried experiments with the in- 

 habitants of those aquatic tents, to ascertain their 

 mode of buildmg. We have deprived them of their 

 little houses, and furnished them with materials foi- 

 constructing new ones, watching their proceedings 

 from their laying the first stone or shell of the struc- 

 ture. They work at the commencement in a very 

 clumsy manner, attaching a great number of chips 

 to whatever materials may be within their reach with 

 loose threads of silk, and many of these they never 

 use at all in their perfect building. They act, indeed, 

 much like anunskilful workman trying his hand be- 

 fore committing himself upon an intended work of 

 difficult execution. Their main intention is, however, 

 to have abundance of materials within reach: for 

 after their dwelling is fairly begun, they shut them- 



* A cement prepared of volcanic earth, or lava. 



