While I was enjoying the sun on a nice summer day in July, this small fly aptly named Litte Snipefly (Chrysopilus asiliformis) caught my attention because of its striking green eyes. Most flies I have encountered had red-dark eyes, so coming across one species that has beautiful green eyes was a nice surprise. The fly I managed to photograph is a female. Like the yellow dung fly (and humans for that matter…), litte snipeflies have differences between the sexes. Females have larger abdomens than their male counterparts. In addition, the eyes of males touch each other (holoptic), while females have plenty of space between their eyes (dichoptic). You can find this in more (though not all) species of flies, including some I highlighted in previous blogs.
Click on the images for more details.
I tried to find out why this sex difference in eyes exists. I haven’t found a clear-cut answer, but my understanding from various sources is that holoptic eyes have more room for visual cells, which will lead to better vision. It could be that males have to rely on their eye sight more than females (for example to hunt, find the best mate or to avoid predators) and thus need bigger eyes. Perhaps they fly around more than females? In another fly species it was found that males and females communicate via pheromones. Male release various pheromones to guide females to them. It may well be that females rely more on scent than on sight and thus have not much need for better vision. Unfortunately, not much is known about the behaviour of litte snipeflies, so it’s all speculation on my part. But who knows, maybe in the future someone might find this interesting enough to conduct a thorough scientific study.
As always, any thoughts or comments are welcome!