Question

I live near a forest with a canal, and often see fruit flies, they also sometimes come in our house and occasionally feed on bits of fruit. Also, sometimes I meet regular house flies here and there, and also in the city I commute to.

I noticed that most fruit flies and alike most often fly in circular shaped trajectories in the air, their curvature of flight contains bends, as if they were riding an invisible rollercoaster all the time. Their flight can be faster or slower, centered around a lamp fixture or near my face eventually, but most importantly, circa 80% of the time I see them flying in this fashion. Also, this is the way I see regular flies flying around, in 99% of cases.

On the other hand, in roughly 20% of cases when I see fruit flies flying, they fly in straight lines, with abrupt and sharp changes in their direction. This is usually (but not necessarily) slower than their rollercoaster way of flying, and it can also be varied regarding how often they change direction abruptly. However, this sharp way of flying is extremely rare in case of the house fly, I have only seen it two times actually, so let's say it happens in 1% of house flies.

What are these distinct flying styles? What is their cause? Are both styles natural and should occur in healthy fruit flies, and house flies as well? Then why is it much rarer in case of house flies? Isn't the sharp style a result of some infection around these animals? Those house flies that I saw flying in the sharp pattern were rather slow anyway, and I saw them in/near my home. Does it occur more rarely in cities?

Answer 1

Fruit flies naturally fly in circular and erratic patterns as adaptive behaviors. These flight styles are due to their genetic makeup and the ecological niche they occupy, with erratic flight less common in house flies likely due to behavioral differences. Genetics and environment shape these behaviors, and are not necessarily indicative of disease.

Step-by-step explanation:

Fruit flies and house flies exhibit distinct flying patterns that are a result of their genetic makeup and adaptive behaviors. The circular or 'rollercoaster' pattern often observed in fruit flies is a natural flight behavior associated with foraging and avoiding predators. The more erratic flight pattern, with sharp turns and straight flights, can be associated with navigation and the avoidance of obstacles or threats, and is less commonly seen in house flies. This is likely due to differences in their ecological niches and behaviors, as fruit flies tend to be smaller and rely more on maneuverability to escape predators. House flies are larger and may rely more on speed. The sharp flying style is not typically a result of infection; rather, it is a natural aspect of their flight repertoire that may be less used due to habitat or behavioral differences.

Comparative studies of fruit flies that have adapted to diverse environments, such as those resistant to cold temperatures, highlight how genetic variations can lead to different physical traits and behaviors. The decreased fecundity seen in cold-resistant fruit flies at early ages compared to flies that are not cold-resistant is likely an energy allocation trade-off where resources are used for cold survival mechanisms rather than early reproduction. This illustrates how traits and behaviors, including flight patterns, can differ within species due to environmental pressures and genetic differences.

Research on Drosophila melanogaster, a common model organism in genetics, emphasizes how particular traits, such as body color and eye color, are inherited according to Mendelian principles. Furthermore, these studies suggest that varying flight behaviors in flies may also be influenced by underlying genetic differences that manifest as observable phenotypic traits. Thus, both the circular and straight-line flight patterns are natural for fruit flies and house flies, reflecting their adaptive responses to their respective environments and life history strategies.