Which of these is not part of insect immunity?
a. Enzyme activation of pathogen-killing chemicals
b. Activation of natural killer cells
c. Phagocytosis by hemocytes
d. Production of antimicrobial peptides

Insect immunity is primarily innate, involving non-specific defense mechanisms. It includes physical barriers, cellular responses like phagocytosis by hemocytes, and humoral responses such as the production of antimicrobial peptides. Unlike vertebrates, insects lack adaptive immunity, which involves specific responses and memory cells.

Phagocytosis is a process where hemocytes, the immune cells in insects, engulf and digest pathogens. This cellular response is crucial for eliminating foreign invaders and is a key component of the insect's innate immune system. Hemocytes act similarly to white blood cells in vertebrates, providing a first line of defense.

Natural killer (NK) cells are a type of lymphocyte found in the adaptive immune system of vertebrates. They play a role in identifying and destroying infected or cancerous cells. Insects do not have NK cells, as their immune system lacks the adaptive component, relying instead on innate mechanisms like hemocytes and antimicrobial peptides.