The title: An August Midnight is more than just a label for the poem, it sets a temporal location for the events and feelings described, pinpointing the time of day and season of the year. The first word, the indefinite article 'An' also has an important role, widening the scope to not just one, but any August midnight.
A shaded lamp and a waving blind,
And the beat of a clock from a distant floor:
The opening lines set a scene using only objects and sounds. The lamp and window blind mark out an interior space; the ticking clock places the scene above or below other interior spaces. These are non-human objects, but they mark out the boundaries of a room, a space that exists for humans. The lamp-shade is a boundary for the source of the light in the room, it hides the glare of the lamp itself and diffuses the light. The 'blind' marks a window boundary, again filtering the light to stop too much getting in or out. They are inanimate themselves, being animated only by the lamp-light or the breeze from outside causing the blind to wave.
On this scene enter -- winged, horned, and spined -
Into the poem now comes a stage direction: the characters, as for a play, arrive on the scene. At first there is no sense of scale: it could be a fabled dragon making its appearance felt.
A longlegs, a moth, and a dumbledore;
Not a dragon, but nocturnal insects making use of the breeze and the open window on a warm August night. The insects are given their vernacular names rather tan the more scientific labels used in the developing science of taxonomy. Now that they are here, we should try to find out a little more about them. The 'long-legs' could be any of a number of members of the Tipulidae superfamily: including Tipula paludosa a common crane-fly in Britain with a habit of entering houses on late summer evenings. Butterflies and moths are both members of the Lepidoptera ordo. The 'dumbledore' is harder to identify: not a headmaster of a fictional school for wizards, but another insect of some kind. According to the Oxford English Dictionary a dumbledore could have been a humble-bee or bumble-bee; also dial. a Cockchafer or May-bug, an insect known for crashing into lighted windows. Beetle, moth and fly, each different from each other. Joining them, already there but unnoticed before is a fly (so a house fly Musca domestica?)
While 'mid my page there idly stands
A sleepy fly, that rubs its hands . . .
'Mid mypage'? Mid my page there are marks of various kinds, letters and punctuation and spaces between them making up a poem. To which there are just two stanzas, each of 6 lines. Each line has four beats. The lines rhyme, but there are different schemes for each stanza: the first rhymes ABABCC, the second has a tighter AABBCC pattern. The rhyme patterns reflect the mood of each stanza: the first more open and distant, the second focussed and reflective.
One word: 'and' appears in each of the first four lines. The whole stanza builds a single sentence. A sentence full of 'ands' as linking words uses a technique called 'hypotaxis': this sentence builds layer upon layer. There is another way of building sense into a sentence 'parataxis' places terms side by side. There is an example of this in the way the insects are introduced: 'winged, horned, and spined'.
Not just words, the punctuation holds the poem together. A comma at the end of the first line, a colon at the end of the second. The third line is interrupted by hyphens and ends with a semi-colon: less strong a connector drawing the unnoticed fly into the conversation. And the stanza ends, but not with a full stop to bring the sentence to a close: a recurring point keeps the stanza open. Just as the hand-washing action of the fly continues and continues to distract the attention
The insects enter the scene as unexpected strangers. Even as insects they are as different from each other as their mammal observer is from each of them. Their presence and behaviour raise questions; perhaps more than can be answered here. The unanswered questions are themselves a source of hope.