Silk trails on Alder

Observation - Silk trails on Alder. Description: Hello Ispot, I have seen a series of silk trails (presumeably from a caterpillar?) on the underside of the main stems of a series of leaning Alder trees. The silks start from c2m and travel into the upper canopy of the trees. There are no obvious 'nest'.

Hello Ispot, I have seen a series of silk trails (presumeably from a caterpillar?) on the underside of the main stems of a series of leaning Alder trees. The silks start from c2m and travel into the upper canopy of the trees. There are no obvious 'nest'. The sil trails are upto 10cm wide. Can any one help me identify the organism responsible.