The mysterious visitor
I first noticed this mayfly (Cloeon dipterum) at rest on my shower screen, having flown in, I supposed, through the open bathroom window. It was tiny but its outline shape caught my eye and prompted me to take a macro photograph to see exactly what it was. I now know it is a Baetidae mayfly, which are among the smallest of mayflies. This one, I would say, was no more than 3-5mm long (excluding the long tails). After photographing it I caught it in a glass and put it out near the pond, thinking (wrongly) this was where it would want to be. The moment I set it free, it disappeared. Returning to the bathroom to collect my camera I saw it had returned, presumably back through the same window! Realising how many predators of small flies there were in the pond (frogs, newts, dragonflies and damselflies to name a few) I decided to leave it where it wanted to be.
I photographed it quite regularly over the next two weeks as it stayed put on the landing (never flying, barely moving at all in fact) until, quite suddenly, it fluttered to be let out at the same window through which it had entered. It looked slightly different now: its eyes (almost entirely white with two narrow brown lines across them, and a tiny black pupil that followed my every move) were now quite black. It left a small mark where it had been stationed on the wall: a spot of dark liquid. The image below shows not only its black eyes as it waits for me to open the window but also, as its head is turned to the camera, its lack of a mouth. Adult mayflies are so ephemeral (most surviving only a day as an adult, others even less than that) they need no sustenance.
On further research it seems likely that this was a female staying away from predators until ready to either lay eggs or give birth. Apparently, the Cloenon dipterum is ovoviviparous, which means (according to Wikipedia) "that the embryos develop into the first larval stage within the eggs while still in the female's oviduct. As a result, the larvae hatch more rapidly, sometimes immediately after egg deposition, and can begin feeding right away."
I suspect, and hope, that she had a short journey, straight down to our pond, and laid them there. What strikes me the most though is what a particularly clever insect this was.
I photographed it quite regularly over the next two weeks as it stayed put on the landing (never flying, barely moving at all in fact) until, quite suddenly, it fluttered to be let out at the same window through which it had entered. It looked slightly different now: its eyes (almost entirely white with two narrow brown lines across them, and a tiny black pupil that followed my every move) were now quite black. It left a small mark where it had been stationed on the wall: a spot of dark liquid. The image below shows not only its black eyes as it waits for me to open the window but also, as its head is turned to the camera, its lack of a mouth. Adult mayflies are so ephemeral (most surviving only a day as an adult, others even less than that) they need no sustenance.
On further research it seems likely that this was a female staying away from predators until ready to either lay eggs or give birth. Apparently, the Cloenon dipterum is ovoviviparous, which means (according to Wikipedia) "that the embryos develop into the first larval stage within the eggs while still in the female's oviduct. As a result, the larvae hatch more rapidly, sometimes immediately after egg deposition, and can begin feeding right away."
I suspect, and hope, that she had a short journey, straight down to our pond, and laid them there. What strikes me the most though is what a particularly clever insect this was.