What astronomical characteristic causes the time the Sun spends traversing Virgo versus Scorpius to differ significantly?

Earth’s orbit is an ellipse, not a perfect circle

The variation in the duration the Sun spends in different constellations is directly attributed to the fact that Earth's orbit around the Sun is elliptical rather than perfectly circular. According to Kepler's laws, this means Earth's orbital speed changes throughout the year. When Earth is closest to the Sun at perihelion (around January), its speed is fastest, causing the Sun to cover the corresponding arc along the ecliptic more quickly. Conversely, when Earth is farthest at aphelion (around July), its speed is slowest, resulting in a longer time spent traversing the arc corresponding to that position, such as the larger segment associated with Virgo (approximately 45 days) compared to Scorpius (approximately 7 days).