INSTINCT OF INSECTS. 487 



not, as Huber expressly informs us'', occur at any marked 

 and regular period, but appears to depend on several 

 circumstances not always combined. Sometimes the 

 bees content themselves with bordering the sides of 

 the upper cells with propolis alone, without altering 

 their form or giving them greater thickness. And it 

 is not less remarkable that, from the instances last 

 cited, it appears that they are not confined to one kind 

 of cement for strengthening and supporting their combs, 

 but avail themselves of propolis, wax, or a mixture 

 of both, as circumstances direct. 



Not to weary you with examples of the modifications 

 of instinct we are considering, I shall introduce but 

 three more :— the first, of the mode in which bees ex- 

 tend the dimensions of an old comb ; the second, of that 

 which they adopt in constructing the male cells and 

 connecting them with the smaller cells of workers ; 

 and the last, of the plan pursued by them when it be- 

 comes necessary to bend their combs. 

 . You must have observed that a comb newly made 

 becomes gradually thinner at its edges, the cells there, 

 on each side, progressively decreasing in length : but 

 in time these marginal cells, as they are wanted for the 

 purposes of the hive, are elongated to the depth of the 

 rest. Now suppose bees, from an augmentation of the 

 size of their hive, to have occasion to extend their 

 combs either in length or breadth, the process which 

 they adopt is this : They gnaw away the tops of the 

 marginal cells until the combs have resumed their ori- 

 ginal lenticular form, and then construct upon their 

 edges the pyramidal lozenge-shaped bottoms of cells, 



" Huber. ii. 284. note ». 



