Why is the presence of hemoglobin in blood important in earthworm but not in insects?

Which organism lives in a more oxygen-deficient environment, you must ask... Earthworms are frequently submerged in stagnant water and, even under good conditions, they have restricted exposure to atmospheric air, living in burrows in the ground as they do. Haemoglobin is more efficient in transporting oxygen than the haemolymph found in insects.