Flammarion L'Atmosphere Météorologie Populaire. 1888.

I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I--
I took the one less traveled by,
And that has made all the difference.

(excerpt) The Road Not Taken. Robert Frost.

In Pilgrim at Tinker Creek, Annie Dillard recounts J. Henri Fabre's observations of the instinctual herding of pine processionaries. Pine processionaries are moth caterpillars which travel through pine trees along a group-generated silk strand. Their bug parade is head-to-rear in one long unbroken procession, hence the name. Fabre noted a troupe of such bugs, stuck for days on the rim of a vase in his greenhouse.

"The caterpillars in distress," he concludes, "starved, shelterless, chilled with cold at night, cling obstinately to the silk ribbon covered hundreds of times, because they lack the rudimentary glimmers of reason which would advise them to abandon it." Annie Dillard quoting Fabre, Pilgrim at Tinker Creek (pp. 67-68)

And what would happen if just one of those bugs had chosen the "road not taken"? Well, as it turns out, a lone caterpillar did navigate off the rim of the vase, a few caterpillars inching forward behind her. Fabre had placed pine needles within reach of these pioneers but it was to no avail. Mere inches from the pine needles they turned and rejoined the group in its caterpillar death march.

These processionaries seem an apt metaphor for the tendency of human groups to act collectively or to hold group beliefs which exhibit little or no individual conscious reflection. (Related terms are mob mentality, groupthink, herding instinct and bandwagon effect.) Fearing retaliation or isolation, desiring to avoid conflict, deferring to authority -- whatever the reason -- human herd behaviors can be just as entrenched as the circling of head-to-rear processionaries. The cycle can be broken when group assumptions are challenged and analyzed. But first it is required that one person consider leaving the metaphorical rim of the vase.