Possible Clues:

• Fungus stood a lot, when cooking
• Mushroom
• Snakes haul back source of poison
• Perhaps midwife's instrument that's potentially harmful if taken?
• Amphibians also left something inedible
• Amphibian's device to produce fungus
• Fungal growth in amphibians, likewise lizards originally
• Lot to do as, running wild, this can be poisonous
• Fungus — a lot stood all around
• Oscar, Bill and Old Bob as well, taken in by retiring lieutenant, recognised by the cap in the forest by mycologist?