In medical entomology, insects that carry pathogens and transmit diseases from one host to another are commonly known as ______.

Introduction / Context:
This public health and biology question focuses on the role of certain insects in spreading diseases. Many serious human diseases such as malaria, dengue, and plague are not caused directly by the insects themselves but by microbes they carry. The technical term for organisms that transport and transmit pathogens from one host to another is widely used in epidemiology. Recognising that these insects are called vectors is essential for understanding disease transmission and control strategies.

Given Data / Assumptions:
- The question asks about insects that transmit diseases. - It implies that these insects carry pathogens between hosts. - Options include pathogens, vectors, drones, and scalars. - Standard epidemiological terms are assumed.

Concept / Approach:
Pathogens are disease causing organisms such as bacteria, viruses, protozoa, and fungi. Vectors are living organisms, often insects or arthropods, that carry these pathogens from an infected host to a new host, facilitating disease spread. Examples include mosquitoes transmitting malaria parasites and dengue viruses, or fleas transmitting plague bacteria. Drones is a term used for male bees in a honeybee colony, and scalars is a mathematical term not related to disease biology. Therefore, insects that transmit diseases are called vectors, not pathogens or any of the other options.

Step-by-Step Solution:
Step 1: Identify the key phrase in the question: insects that transmit diseases. Step 2: Recall that the organisms causing the diseases are pathogens such as Plasmodium or viruses, not the insects themselves. Step 3: Remember that insects like Anopheles mosquitoes can take up pathogens from an infected person and pass them on to another person during feeding. Step 4: Recognise that such disease transmitting organisms are called vectors in epidemiology. Step 5: Note that drones are male bees in a hive and are not defined by disease transmission. Step 6: Note that scalars is a mathematical term referring to quantities with magnitude only and has no biological meaning in this context. Step 7: Conclude that the correct term for insects that transmit diseases is vectors.

Verification / Alternative check:
Health education materials about malaria and dengue frequently describe the mosquito as a vector. The phrase vector borne diseases is widely used to refer to diseases spread by mosquitoes, ticks, and other arthropods. In contrast, pathogens are listed separately as the actual causative agents, like the malaria parasite Plasmodium species. Academic texts on epidemiology and public health also define vector as an organism that transmits a pathogen from one host to another. This consistent use confirms that vectors is the correct answer.

Why Other Options Are Wrong:
Pathogens: These are the disease causing microbes themselves, not the insects that carry them, so this option does not match the question. Drones: This term refers to male bees in a hive and is unrelated to disease transmission in humans. Scalars: This is a mathematical concept and has no role in describing insects or disease transmission.

Common Pitfalls:
A common error is to confuse the insect carrier with the disease agent itself and pick pathogens. Another pitfall is not paying attention to context and choosing a familiar but irrelevant term. To avoid mistakes, always distinguish between the pathogen, which actually causes the disease, and the vector, which transports the pathogen. Associating the term vector with mosquito in malaria or Aedes in dengue helps anchor the correct concept in memory.

Final Answer:
Insects that transmit diseases are known as Vectors.