In Chapter 12, Darwin describes many possible ways plant seeds might be dispersed around the world. He uses a simile and imagery as he describes a swarm of locusts that may have introduced invasive plant species to Madeira through seeds in their dung:
The Rev. R. T. Lowe informed Sir C. Lyell that in November, 1844, swarms of locusts visited the island of Madeira. They were in countless numbers, as thick as the flakes of snow in the heaviest snowstorm, and extended upwards as far as could be seen with a telescope. During two or three days they slowly careered round and round in an immense ellipse, at least five or six miles in diameter, and at night alighted on the taller trees, which were completely coated with them.
Darwin does not simply state that a swarm of locusts visited Madeira in 1844. Instead, he impresses upon the reader how awe-inspiring the sight of the locusts was, at least to the man who wrote to Charles Lyell about the swarm. Darwin compares the "thick" swarm of insects to the "flakes of snow in the heaviest snowstorm." This simile not only gives the reader a sense of what the swarm looked like, but also associates the swarming of locusts with big climate events, such as "the heaviest snowstorm." Darwin is trying to suggest a natural interdependence between insects and plants. If a swarm of locusts is as natural and consequential an event as a snowstorm, it follows that locust swarms might be part of the broader story of natural selection and plant species' fight for survival.
The simile fits into the broader set of images Darwin uses to describe the locusts. He claims that the cloud of insects extended upward past what could be seen with the naked eye. He describes the constantly buzzing, "immense ellipse" they formed as they flew overhead for 2 or 3 days, and he describes how they completely encased the tall trees at night. This imagery is not necessarily an exaggeration. Locust swarms really can be classified as a natural disaster in some cases. But the way Darwin pauses over these images is notable given that his book is more scientific and academic than literary. By emphasizing the impressive sight of the locust swarm, Darwin captures his readers' attention and shows them just how overwhelmingly powerful and violent nature can be. Given that his thesis holds that natural forces are entirely responsible for the creation of all simple and complex life forms, these images help Darwin convince his readers that nature is as powerful as it needs to be for his theory to hold true.
In Chapter 14, Darwin describes a beetle that hatches in bees' nests, eats bees' eggs while in the larval stage, and changes its appearance to look more like bee larvae until it is nourished enough to emerge as a perfectly formed beetle. He uses imagery in his description:
As soon as the female bee deposits her eggs on the surface of the honey stored in the cells, the larvæ of the Sitaris leap on the eggs and devour them. Afterwards they undergo a complete change; their eyes disappear; their legs and antennæ become rudimentary, and they feed on honey; so that they now more closely resemble the ordinary larvæ of insects; ultimately they undergo a further transformation, and finally emerge as the perfect beetle.
Darwin uses accurate scientific terms like "Sitaris," "larvae," and "antennæ," but otherwise he stays away from dry language. His choice to use verbs like "leap" and "devour" as he describes the beetles' invasion of the bees' nest turns this natural observation into an action scene. By the time Darwin gets to the actual transformation in the beetles' form, the reader is imagining them not in a sanitized laboratory, but rather in nature, surrounded by buzzing bees. The transformation almost invokes horror: the beetles have eaten the bees' young and are secretly morphing into changelings so that the bees are forced to nourish the very murderers of their own children. Of course, the emotional drama of all this is a human projection onto the insects. Darwin uses imagery to invite this projection. Not only does it keep readers' attention, but it also helps animate the idea, central to Darwin's theory, that nature is brutally competitive.
