Distinguish between parous and nulliparous females and why parity data are useful.

• A. Parous are male mosquitoes; nulliparous are female.
• B. Parous have never laid eggs; nulliparous have laid eggs.
• C. Parous have laid eggs; nulliparous have not; parity data indicate age structure and potential for transmission.
• D. Parous are always older than a year; nulliparous are younger.

Answer: (C)

Distinguishing parous and nulliparous females centers on reproductive history: parous have laid eggs, nulliparous have not. The determination is usually made by dissecting the ovaries to look for signs of a prior oviposition cycle.

This history matters because parity data reveal the age structure of the female population. Older, parous females have had more time to take infectious blood meals and to allow pathogens to reach the stage where they can be transmitted, so a higher proportion of parous mosquitoes signals greater potential for disease transmission. Conversely, a population with more nulliparous individuals is younger and typically carries a lower immediate transmission risk. Parity data also help estimate survival rates and feed into models of vectorial capacity, and they provide a way to assess how well control measures are reducing the lifespan of the mosquito population.

Other statements don’t fit because parity concerns reproductive history in females, not sex; parous are not defined as having never laid eggs; and parity is not a fixed age category like “older than a year” but a record of whether an egg-laying event has occurred.