elongates

As the hind foot elongates the index will increase; elongation of the hind foot is interpreted as a specialization.

As the tail elongates the index decreases and as the tail becomes shorter the index increases.

To give the first bite the caterpillar elongates its body, and carries its head as far forward as possible.

The proboscis of the male is about a foot long when the creature is at rest, but elongates under excitement.

Then a thick thread is emitted from one or both extremities, which elongates and becomes branched in a pinnate manner.