Blood in Earthworm
Earthworms are invertebrates that belong to the phylum Annelida. They have a closed circulatory system, meaning that their blood is confined to vessels and does not freely flow through body cavities. The blood in earthworms is called hemolymph, which serves various functions within their body.

Composition of Hemolymph
Hemolymph in earthworms is composed of plasma and various cells called hemocytes. Unlike in humans and other vertebrates, earthworms do not have red blood cells or erythrocytes.

Hemocytes in Earthworms
Hemocytes are the main cellular component of the earthworm's hemolymph. They have a role in the immune response and the clotting process. Hemocytes are colorless cells and are responsible for the transport of oxygen and nutrients throughout the earthworm's body.

Color of Hemolymph
Although the blood cells in earthworms are colorless, the hemolymph itself may appear reddish due to the presence of other pigments. One such pigment is hemoglobin, which can bind to oxygen and is responsible for the red color of blood in many animals. However, it is important to note that earthworms do not have specialized structures like red blood cells to transport oxygen.

Comparison with Other Animals

- Cockroach: Cockroaches have a tubular heart and an open circulatory system. Their blood, called hemolymph, contains colorless plasma and various types of cells, including hemocytes. However, cockroaches do not have red blood cells.
- Birds: Birds have red blood cells that contain hemoglobin, giving their blood a red color. The blood cells in birds are responsible for the transport of oxygen.
- Bedbug: Bedbugs have a closed circulatory system, and their blood, called hemolymph, contains colorless plasma and various cells. However, they do not have red blood cells.

Conclusion
In conclusion, earthworms have hemolymph that appears reddish due to the presence of pigments, but they do not have red blood cells. The absence of red blood cells is a characteristic feature of earthworms and some other invertebrates.