What is a primary function of the proboscis in adult mosquitoes?

The primary function of the proboscis in adult mosquitoes is indeed to pierce skin and suck blood. The proboscis is an elongated mouthpart that has evolved specifically to allow mosquitoes to efficiently feed on the blood of their hosts. When a mosquito feeds, it uses the sharp tip of the proboscis to penetrate the skin, allowing it to access blood vessels. In addition to blood, the proboscis can also be used to consume nectar, which is a food source for many mosquitoes, but this function is secondary compared to its role in blood-feeding.

The design of the proboscis includes specialized structures that help the mosquito navigate through the host's skin. This adaptation is crucial for survival and reproduction since female mosquitoes require blood to develop their eggs.

While some of the other options listed may seem plausible in a broader context, they do not directly relate to the main function of the proboscis in adult mosquitoes. For example, filtering water is not relevant to the feeding function of the proboscis, as mosquitoes do not use it for that purpose. Regulating body temperature is also not a function associated with the proboscis itself, and therefore, it does not play a role in this context.