Alot of ourcaterpillers haven't gone up into trees but, are stopping on the trunks. What's wrong with them?

Question

Some of them have gone into or are just starting there cacoons. Some of the others are just sitting on the trunks of trees and not really doing anything. Is something wrong with them?

Answer 1

Without knowing what type of caterpillar, or where you're located, all I can do is give you some possible causes.

If your weather has been cool and wet, it's possible that they're being affected by a natural virus (nucleopolyhedrosis virus or NPV) or fungus (such as Entomophaga maimaiga, used to control gypsy moths, but other species are susceptible) that's slowly killing the caterpillars which are stopping along the trunk.  There are also bacteria (Bacillus thuringiensis) and protozoan parasites that could affect them.  

Some types of caterpillars will make cocoons under loose bark, or in the crevasses of deeply furrowed bark, but if you're familiar with they type and notice that these should be going into the outer branches to make their cocoons, I'd take this as a sign that the ones not reaching the normal areas are being affected by one of the other possible causes.