Archips is a common, patch-restricted forager that feeds socially on small cherry trees. The caterpillars live in colonies containing several hundred siblings but colonies may merge, resulting in aggregations of a thousand or more individuals.
 
 

Upon hatching from the egg mass, which is deposited at the base of the tree near the ground the previous year, the caterpillars move to the tip of the tree to form the nucleus of their nest.  As the move up the stem, the caterpillars lay down silk trails.  It has been shown that a chemical component of the silk elicits trail following.   The caterpillars may also make occasional excursions to other parts of the tree if the original nest site proves inadequate and in the process they mark trails which facilitate the reaggregation of the colony at a new site

Perhaps the most remarkable aspect of the caterpillar's collective behavior is their ability to manipulate leaves and branches, drawing them into a compact nest within which they live, feed, and ultimately pupate. They accomplish this by spinning silk threads between the existing nest and new leaves that are to be drawn into the nest.  Each stand of silk is stretched slightly before it is attached to a leaf and its axial retraction exerts a miniscule force on the leaf, pulling it slightly toward the nest.  It is the cumulative force of many such strands of silk spun by groups of caterpillars all spinning at the same time that eventually draws the leaf into the nest.  In this way the entire top of a small tree may be tightly bound into a nest.

When the larvae have finished feeding, they constuct  pupal cells at the center of the nest where large quantities of accumulated frass are held together with silk, forming a tube.  A section of  this  "central pupal chamber" is shown at the right.

Fitzgerald, T. D. 1993. Trail and arena marking by caterpillars of Archips cerasivoranus (Lepidoptera: Tortricidae). J. Chem. Ecol. 19:1479-1489.

Fitzgerald, T. D., K. Clark, R. Vanderpool and C. Phillips. 1991. Leaf shelter-building caterpillars harness forces generated by axial retraction of stretched and wetted silk. J. Insect Behav. 4: 21-32.

Fitzgerald, T. D. 1995.  Caterpillars roll their own. Natural History Magazine 104:30-37