INSTINCT OF INSECTS. 



393 



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 sup- 

 porting 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 extend the dimen- 

 sions 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 becomes 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 mar- 

 ginal 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 oc- 

 casion 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 

 original lenticular form, and then construct upon their edges 

 the pyramidal lozenge-shaped bottoms of cells, upon which 

 the hexagonal sides are subsequently raised, as in their 

 operation of cell-building. This course of proceeding is in- 

 variable : they never extend a comb in any direction what- 

 ever without having first made its edges thinner, diminishing 

 its thickness in a portion sufficiently large to leave no angular 

 projection. Huber observes, and with reason, in relating 

 this surprising law which obliges bees partially to demolish 

 the cells situated upon the edges of the combs, that it deserves 

 a more close examination than he found himself competent to 

 give it ; for if we may to a certain point form a conception 

 of the instinct which leads these animals to employ their art 



