Spring
Spring is the most important metaphor in the book and it is even mentioned in the title. Spring it is generally associated with the idea of rebirth and life but here, the adjective "silent" added before it suggests that man influenced nature in a negative way and affected the natural way of things. As a result, spring no longer symbolized the lively season but was rather associated with death. Thus, the silent spring is used here as a metaphor to suggest death and decay.
The dress of Medea
In the third chapter, the author compares the way pesticides affect plants with a mythical dress. In Greek mythology, there exists a dress that Medea gave to one of her rivals. The dress however was poisonous and it ended up killing the person who wore it. In a similar way, pesticides made plants poisonous and dangerous to the pests. Thus, when a pest ate a plant, that pest died. However, the process cannot be controlled and so many animals ended up eating the affected plant and died as a result. The comparison has the purpose of emphasizing the idea that such a tactic is not only hard to control but can have catastrophic effects.
Like a nuclear weapon
The author compares the way pesticides and herbicides affect the environment and the population with the way nuclear weapons affects the population. The comparison between the two is used here to emphasize the idea that when man tries to disrupt the natural way, he can damage the environment beyond anything he can imagine and he can also damage himself in the process.
A dangerous toy
In the 6th chapter, the author compares weed-killers with dangerous toys the farmers and those who use them don’t fully understand. The weed-killers give the impression that the human using them is powerful but in reality, they end up doing more harm than good and affects the environment in ways humankind could not have imagined. The comparison has the purpose of highlighting the idea that more than often, farmers and pesticides and herbicides producers think too lightly about their products.
Metaphor for death
An aspect mentioned time and time again is that birds and other animals became infertile after being exposed to pesticides. As a result, the population of certain species dropped drastically in time. The lack of new fledglings and the sterility problems are used here as a metaphor for death as they ass suggest that man has disrupted the natural way of things and what resulted was something catastrophic.
