Why Caterpillars Crawl Up Tree Trunks

The Journey from Egg to Leaf

Seeing "convoys" of caterpillars ascending tree trunks is common in spring. They're not lost—they're following their life cycle.

Egg Placement Matters

Adult moths and butterflies lay eggs on leaves, but sometimes deposit them on bark instead. When eggs hatch on the trunk, the tiny larvae must crawl upward to reach their food source: the foliage.

No Cause for Alarm

This behavior is normal for many species, including tent caterpillars and cankerworms. Most trees tolerate moderate defoliation. If infestations are severe, apply Bacillus thuringiensis (Bt) when caterpillars are small.

Understanding the "why" turns a creepy sight into a fascinating nature observation.