Synchronized twitching

The fall webworms' silk nest forms a formidable defense; however, the caterpillars do not always rely on the protective layer alone.

A dense group of fall webworms (Hyphantria cunea) inside a silk nest.

In order to construct and extend the sheets of silk, some of the caterpillars spend time exposed on the outside of the nest. There, they take advantage of their numbers to defend themselves in another way -- by making a coordinated, threatening display. 

The synchronized action of the caterpillars is thought to discourage predators and parasites.  Though the twitching sometimes appears to begin spontaneously, it can also be triggered when something approaches the caterpillars.  For example, in the video above, the last bout of twitching appears to be in response to the arrival of a small fly or wasp on the other side of the nest (~1:44).

On the safe side

When feeding in a large group, caterpillars may be more noticeable to predators -- but they may also be better able to defend themselves.  Groups of tent caterpillars and webworms can consist of hundreds of individuals, which makes them easily spotted (and probably smelled) even from a distance. To thwart their many enemies, these caterpillars surround themselves and their feeding zones with a protective netting of silk.

A nest of fall webworms (Hyphantria cunea) on a mulberry branch.

The caterpillars then proceed to devour nearly everything within their tightly woven nest.  As they move along a branch, all that they leave behind are leaf skeletons wrapped in silk.

The larvae can completely skeletonize large leaves.

Meanwhile, any predators that locate the caterpillars are likely to depart without obtaining a meal. Watch a wasp get foiled by the silk enclosure in the video below:

This place is hopping, part two

The water covering the ground gradually drained and evaporated away, slowly enough that the swarms of tadpoles had a chance to make the transition to a more terrestrial lifestyle.  Many of them still had a lot of growing left to do, though.

A toadling in the leaf litter.

As I walked through the forest, I kept sending waves of tiny toads hopping for cover.

A closer view of the toadling.

They were so small and well camouflaged in the leaf litter that they would easily have been overlooked if they had just remained still.

Another toadling blending in with the leaf litter.

However, the toadlings on the path through the woods faced a different problem.  They could not hop quite enough.  The raised edge of the trail proved too high an obstacle for their small legs, trapping them until they found some place to squeeze through.

A toadling thwarted by the edging of the trail.