and even, it seemed, the lean bare-backed downs, sent the moth fluttering from side to side of his square of the windowpane."  Woolf suggests that within the moth's construction of being were the limitless "possibilities for pleasure."  Over the course of the metaphor, Woolf sees the metaphorical connection between the struggle for life as something that human beings exhibit in their own conditions.  Woolf does not miss the chance out how the moth's fight for life is applicable to more than the world of animals: 

Being intent on other matters I watched these futile attempts for a time without thinking, unconsciously waiting for him to resume his flight, as one waits for a machine, that has stopped momentarily, to start again without considering the reason of its failure. After perhaps a seventh attempt he slipped from the wooden ledge and fell, fluttering his wings, on to his back on the windowsill. The helplessness of his attitude roused me. It flashed upon me that he was in difficulties; he could no longer raise himself; his legs struggled vainly.

The idea of the moth who "struggled vainly" is representative of how modern consciousness has "shifted" in terms of the struggle intrinsic to existence in the world.  That is communicated in the metaphor of the moth:  

The body relaxed, and instantly grew stiff. The struggle was over. The insignificant little creature now knew death. As I looked at the dead moth, this minute wayside triumph of so great a force over so mean an antagonist filled me with wonder. Just as life had been strange a few minutes before, so death was now as strange. The moth having righted himself now lay most decently and uncomplainingly composed. O yes, he seemed to say, death is stronger than I am.

When Woolf speaks of the "shift" in "conduct," she is suggesting that one of the critical aspects of Modernism is the individual's relationship to their own mortality.  This shift in "conduct" defines us, as it does Woolf in her essay, because we become aware of forces larger than us.  Just as the moth concedes, we, as human beings, live life only to understand how death is "stronger" than we can ever hope to be.  Woolf uses the metaphor of the moth to communicate how conduct changes when, like the "insignificant little creature," we become knowledgeable about death.

Woolf's use of the moth metaphor is extremely important.  The thesis that Woolf is suggesting is life and conduct is fundamentally changed in the modern setting.  The awareness of the forces that weigh down represents a type of "shift" in "human relations."  Her thesis is enhanced with the use of the metaphor.  The detailing of the life energy that the moth once had shifts to a setting where it concedes defeat in the face of death.  Woolf suggests that this experience is something that human beings themselves experience in the modern setting.  

This thesis is enhanced through the depiction of the moth's experiences.  The development of the metaphor from a state of limitless energy to one where life is taken by the force of death is critical to the essay. In tracing this evolution of the moth towards its finality, Woolf seeks to illuminate an aspect of the human condition, a reality that highlights this "shift" in "conduct" that Woolf believes underscores the modern setting.  Woolf's relationship to the moth changes over the course of the essay. She recognizes the moth's entrance as almost an afterthought.  Yet, in seeing its struggle and eventual acquiescence to death, Woolf understands more about the human predicament and her own.  The distance that Woolf shows in the start of the essay changes by its end, a reflection of how the metaphor has impacter her own capacity as narrator and artist:

It was useless to try to do anything. One could only watch the extraordinary efforts made by those tiny legs against an oncoming doom which could, had it chosen, have submerged an entire city, not merely a city, but masses of human beings; nothing, I knew had any chance against death. 

The tenor of the shift in consciousness is illuminated through the vehicle of the moth's death.  Woolf is able to illuminate her conceptual tenor through the moth vehicle, and in the process, highlights how all human existence has much in common with that of the moth.  It is this idea, the idea of how fragile life is, that drives the essay.  This concept is the point of struggle within the essay because it is the point of struggle in Woolf's own understanding.