It is now more necessary than ever.

All contribute to it from the produce of their spinnerets, as is the invariable rule whenever there is a progression.

Not one takes a step forward without fixing to the path the thread from his lips.
If the series forming the procession be at all long, the ribbon is dilated sufficiently to make it easy to find; nevertheless, on the homeward journey, it is not picked up without some hesitation.

For observe that the caterpillars when on the march never turn completely; to wheel round on their tight-rope is a method utterly unknown to them.
In order therefore to regain the road already covered, they have to describe a zigzag whose windings and extent are determined by the leader's fancy.

Hence come gropings and roamings which are sometimes prolonged to the point of causing the herd to spend the night out of doors.