The Origin of Species · Chapter
Slave-Making Instinct explained
Darwin examines the remarkable slave-making instinct in ants, focusing on Formica rufescens and Formica sanguinea.
What happens
Darwin examines the remarkable slave-making instinct in ants, focusing on Formica rufescens and Formica sanguinea. He describes Pierre Huber's observations of F. rufescens, which is entirely dependent on its slaves for survival, and his own detailed observations of F. sanguinea in England. Darwin notes differences in slave reliance between Swiss and English populations, and speculates on how the instinct might have evolved through natural selection from the habit of carrying off pupae for food.
Themes in this chapter
Natural Selection and the Struggle for Existence
Darwin uses the slave-making instinct to illustrate how natural selection could perfect a complex behavior, starting from the simple habit of carrying off pupae for food.
Adaptation and the Utilitarian Doctrine
The instinct is shown to be of clear utility to the species, with each modification being advantageous, leading to extreme dependence in Formica rufescens.
Characters to notice
- Pierre Huber
First discovered the slave-making instinct in Formica (Polyerges) rufescens; described as a better observer than his celebrated father.
- Mr. F. Smith
Provided information on the habits of Formica sanguinea in England; observed that slaves are strictly household slaves.
- Charles Darwin
Conducted detailed observations of Formica sanguinea nests in Surrey and Sussex, including witnessing a migration and slave-making raids.
Key passages
“This remarkable instinct was first discovered in the Formica (Polyerges) rufescens by Pierre Huber, a better observer even than his celebrated father.”
Pierre Huber, an even keener observer than his famous father, first identified the slave-making instinct in the ant Formica rufescens.
Introduces the discoverer and the ant species central to the chapter.
“What can be more extraordinary than these well-ascertained facts? If we had not known of any other slave-making ant, it would have been hopeless to speculate how so wonderful an instinct could have been perfected.”
These well-documented facts are astonishing; without knowledge of other slave-making ants, it would be impossible to guess how such an instinct evolved.
Highlights Darwin's amazement and the importance of comparative evidence for understanding instinct evolution.
“If their presence proved useful to the species which had seized them—if it were more advantageous to this species, to capture workers than to procreate them—the habit of collecting pupae, originally for food, might by natural selection be strengthened and rendered permanent for the very different purpose of raising slaves.”
If captured foreign ants proved beneficial, making it more advantageous to capture workers than to raise their own, the original food-gathering habit could be reinforced by natural selection into a permanent slave-making instinct.
Darwin's hypothesis for the evolutionary origin of the slave-making instinct.