caterpillars of birch sawfly craesus septentrionalis larvae feeding on willows leaves

animal betula birch black caterpillar close closeup disease environment fenusa fly forest garden green herbivores hymenoptera insect insects invertebrate larva larvae leaf leafminer leaves macro miner natural nature parasite parasitic patch pathogenic pest plant planteating poop protection pusilla rattle sawfly seperate sound stage tree wasp wild wildlife wormlike yellow