118 SIR JOHN LUBBOCK ON ANTS, BEES, AND WASPS. 



Observations on Ants, Bees, and Wasps. — Part XI. 

 By Sir John Lubbock, Bart., M.P., D.C.L., LL.D., F.E.S. 



[Kead 1st December, 1887.] 



On the Relation between Formica sanguinea and 

 ITS Slaves. 



It is well known that Polyergus rufescens is entirely depend- 

 ent on its slaves. Huber long ago found tliat this ant will 

 starve in the midst of plenty, and will not even put food into its 

 own mouth. I have shown that isolated specimens will live for 

 months if they are allowed a slave for an hour or so every two or 

 three days to clean and feed them. It is said, on the contrary, 

 that our only slave-making species, Formica sanguinea, can 

 manage without slaves. Indeed, it appears that nests are 

 sometimes found in which there are mistresses alone, entirely 

 without slaves, Forel thinks that he has observed in such 

 nests generally a larger proportion of small individuals than 

 in nests which possess slaves. This would be interesting as 

 lending to show that in such nests the young are less well 

 nourished than when they have slaves to attend upon them. 



The question remains, of what advantage are the slaves to the 

 F. sanguinea ? Forel says, I do not quite understand why, " Je 

 ne veux pas trop rechercher le motif qui pousse les sanguinea a 

 se faire presque toujours des esclaves." " Peut-etre," he adds, " le 

 sentiment de leur force, et le desir de travailler moins, pour faire 

 plus a leur aise la chasse aux Lasius flavus et L. niger, est-il le 

 mobile qui les pousse a cet acte. Celui-ci leur serait pen a peu 

 devenu plus ou moins instinctif puisqu'il etait avantageux a 

 la conservation de leur espece." This suggestion seems very 

 probable, and may be partially correct ; it is not, however, 

 I think, a complete explanation. I have had under observation 

 several nests of F. sanguinea. One of them I owe to the kind- 

 ness of M. Forel himself, who sent it to me in June 1882. 

 There was no queen, and, though the nest was very healthy, of 

 course the numbers gradually diminished. At the beginning 

 of January 1886 the last slave died, and there then remained 

 only about 50 F. sanguinea. Under these circumstances the 

 sanguinea began to die off rapidly ; by the middle of the year 

 only six remained alive, and these, no doubt, would not have 

 survived long. On July 1st I got some pupae of F.fusca and 

 placed them outside the nest. The sanguineas soon discovered 



