How do you tell the gender of a horsefly?

To determine the gender of a horsefly, observe the eyes: male horseflies typically have large, bulging eyes that meet at the top of their heads, while female horseflies have more widely spaced eyes. Additionally, males are usually smaller than females and may have more colorful markings. Female horseflies also possess a more robust body and are the ones that bite, as they require blood for reproduction.