Judging from the specific terms searched for, it appears that many of these searchers are doing so because they have been given an assignment to interpret her poem 'The Warning'. So I thought I'd have a go.
1 Just now,
2 Out of the strange
3 Still dusk . . . as strange, as still . . .
4 A white moth flew. Why am I grown
5 So cold?
It is a characteristic of Crapsey's work that she manages to condense a great deal of meaning into a very short form, and evokes very specific locales (as Alkalay-Gut notes about the poem 'Niagara'). To deal with practicalities first: it is dusk (l3), in autumn (moth in l4) she is indoors ("out" in l2), looking through an open window (moth flew in: l2). But this is not a single moment in time: there is an implied sequence of events, which goes: I dusk II moth flies into room III poet becomes cold.
This prepares us to look at the more mysterious elements in the poem. In l3, we have the fragmentary "as strange, as still", echoing the "strange still dusk" of l2&3, which requires as a complement "as strange, as still, as something", something like an autumn dusk, an ending, a quietude: Death. The moth is The Warning of the title, of the coming of death.
Why would a moth fly into the room? To go towards a light or a flame. What was in the room that would attract it? Possibly a real lamp, but possibly not. In lines 4 and 5, stage III of the sequence, the poet's body is becoming cold in a way that is mystifying to the poet. What is happening? The spirit is leaving the body after death. It is the light of spirit that attracted the moth; the warning is not of approaching death, but of the start of the after-life.
It would be easy to read the poem as mundanely autobiographical; no doubt in her last year, dying of tuberculosis and writing cinquains, she did indeed often sit with the window open to the evening, despairing. (As an aside, in the 1930s it was discovered that TB bacteria could not survive in cold dry air, leading to the creation of "Fresh Air" hospitals where TB patients' beds would be wheeled outside during the day, and large windows would be left open whenever possible [ BBC story ]. Crapsey died before this).
But the poem is better than that. It is a warning to all that time is short, and a reckoning will come. Let that guide your life.
Virginia Woolf, probably independently of Crapsey, wrote about moths and death in The Death of the Moth :
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.
A note to students. This is MY interpretation, not yours. And it might not get many marks, anyway.