Further in Summer than the Birds — Periodical Cicadas

The long life cycle of cicadas can be 13 or 17 years, but never 15. This was observed in Dickinson's time without known the reason. Cicadas mate in group, lay eggs and die, a scene described in this poem.

Further in Summer than the Birds 1
Pathetic from the Grass
A minor Nation celebrates
Its unobtrusive Mass.

No Ordinance be seen 5
So gradual the Grace
A pensive Custom it becomes
Enlarging Loneliness.

Antiquest felt at Noon 9
When August burning low
Arise this spectral Canticle
Repose to typify

Remit as yet no Grace 13
No Furrow on the Glow
Yet a Druidic Difference
Enhances Nature now
(F.895/J.1068)
[1] Summer:: with reference to prosperous, pleasant, or genial conditions (OED 4e). Further in Summer than the Birds:: via the Mass (mating), the cicadas extend their prosperous life further than the birds.
[2] Pathetic:: cicadas will die after the mating Mass.
[3, 4] minor Nation, Mass:: a group of cicadas mate at the same time as a Mass.
[5, 6] No Ordinance, gradual:: no ordinance but advancing slowly.
[7] pensive Custom:: male cicadas die soon after mating.
[8] Loneliness:: female cicadas are alone and will die after eggs laid.
[9] Antiquest:: the oldest propagation process. Noon:: the highest moment of the Mass.
[10] August:: eminent, majestic. burning:: the state of being inflamed with desire.
[11] spectral Canticle:: sounds produced by cicadas.
[12] Repose:: to idle; cicadas will idle themselves for many years. typify:: to exhibit this essential character (the odd life cycle).
[13] Remit, no Grace:: the mating remits life with the cost of death, which is no grace.
[14] No Furrow on the Glow:: a passionate gathering without trace. The female cicadas lay eggs into the bark of trees.
[15] Druidic Difference:: indicating the mystic difference of 13 and 17; no answer to these numbers in Dickinson's time.
[16] Enhances Nature:: enhances the greatness of world's nature.

Divergent Evolution in the Periodical Cicada. In this species we have examples of two quite distinct divergences, each depending on its own forms of Segregation, which are easily recognized. The life-history of this insect covers 17 years and one or two months. The imago appears late in May, and for a little more than a month the males make the woods ring with their shrill stridulations. The eggs, which are deposited in the green twigs of trees, mature during the latter part of July; and each newly-hatched larva dropping to the ground, takes up a solitary subterranean life, which it follows till its period of 17 years is nearly complete. It then appears above the ground, passes into its winged stage, and enters on a few weeks of social life which closes its career. This species is widely distributed in that part of the United States that lies between the Atlantic shore and the Rocky Mountains. It does not, however, occur in Minnesota, Northern Michigan, or Northern New England. It is, however, represented by two races in every respect the same, except that one has a life-history of thirteen and the other of seventeen years. . . . and, even if our informants are mistaken in supposing that cross-unions do not occur, there must be some form of incompatibility between the two races, resting on divergent endowments; for otherwise we should find hybrid descendants with periods of more than 13 and less than 17 years' duration. ─ Annals of the Lyceum of Natural History of New York (1856)