Yesterday’s posting about an Orgy in Nelson speculated that the participants were mayflies, and that, owing to their short lives, it was a one-night event. The pictures from the next evening showed I was wrong on the second point, and a couple of people challenged the first, suggesting the insects were really caddisflies.
See the comments, below, where it is finally determined that these insects are caddisflies.
Actually, it dawned on me yesterday, that even if mayflies only lived a few hours, there could be a different batch swarming the following evening, so I took a look and there they were (pictures below).
But, are these mayflies or caddisflies? It seems that both species will do this sort of thing. The only way to be sure is to collect some spent ones on the ground. I failed to find any.
Could one settle the issue from the pictures showing them flying around distant tall trees? Possibly, but to do so unambiguously would require a better camera than I have. At best, about all one might distinguish is the difference in the shape of the wings: a mayfly’s wings are widest near the body (proximal); a caddisfly’s are widest near the tips (distal). With each cover picture, below, I include a detailed shot (full-resolution crop) from a random location within the swarm. Admittedly, there are ambiguities, but it looks as if the wings are widest near the body, and so maybe they are mayflies. But, the jury is out.
Either way around, being in a swarm enables them to spend their short adult lives mating.
The ability to even see the swarm strongly depends upon the lighting and the background. When this same group of insects was seen against the sky rather than the mountain, they seemed to vanish.
In a detail of a random portion of the above picture, wing shapes are sometimes evident.
Another tree and another image followed by a detail.
Finally, a pair of backlit pictures (shot in the general direction of the Sun).
