My Night-Time Buddies!

The Summer monsoon weather pattern has been hanging on for dear life - "good for the corn" as they used to say in the Midwest with near-daily clouds and rain, but bad for the stars and photon-deprived amateur astronomers around here! What is an observer of the universe expected to do? Well, like in Illinois when I switch to lookin' at bugs in the backyard, there are similar subjects here in Tucson. Fortunately, late monsoon season is a good time for the spectacular flowers of cereus repandus - night bloomers with flowers up to 15cm (6") in diameter! It is sometimes tough to tell very far in advance when they'll bloom - at left is one about to open, shown near sunset. Yet a mere 3.5 hours later, it is transformed to the image at right.

But while the flowers are beautiful, what is interesting to me are the visitors that come by during the night. Almost magically, about a half hour after fully opening, the moths start drifting in to feed on the nectar and help pollinate the plants. It is the transitory appearance that is of interest to me. I've blogged about them many times, starting with the time-lapse I made back in 2012. Back then taking only 20 frames/hour, I was lucky to catch one moth during the night.  Close examination of the time lapse indicated from flower movement that many more were visiting while not exposing. Since then I've upped the frame count up to 240 per hour and now am seeing 20 or more during the night - a busy location indeed! Something to note is what they accomplish during the night - at left is the near-virginal flower enlarged from the right image above. Note the clean greenish central stigma, and the anthers loaded up with pollen. Of course, far down the throat of the flower is where the nectar is located that the moths crave. The image at right shows the stigma after only 8 moth visits over the course of an hour.  The sticky stigma is "dirty" with the shed scales of the moth, as well as pollen from this as well as other plants carried by the pollinators.

Over the course of the night this continues with dozens of moth visits. The large tubular flowers require pollinators with a long proboscis to reach down the flower to where the nectar is located deep in the flower. Note the long probes of the moths seen (and blogged) previously here, as well as here. This year I might have caught my best proboscis picture, shown at left. You can see the length exceeds their wingspan by a considerable amount. You can also see how far in they "attack" the flower - from the image at right (a different moth) they can reach considerably far down the neck of the flower!  Note also the moth at right has some wing damage - it doesn't seem to affect its flying characteristics much, and would actually serve a useful purpose to identify future visits to the yard...

And if you'll indulge me a few more images (got lots of 'em now!) at left is another great proboscis shot, though the moth is mostly out of focus. Still, you would think they have to be careful as they come in for docking - damaging that thing would likely affect its feeding significantly! At right is the best view I've had of the proboscis base - note that it is actually a pair of tubes! I've not noticed this before, nor know the purpose, but find it quite interesting... Almost all of these images that includes their eyeballs shows a "catseye" effect. If you shine a flashlight or take a picture of them, the lens focuses the light on their retina and there is a beam that comes directly back to the viewer. It is an easy way to find your cats in the dark yard - shine your flashlight around and look for the glow from their eyes. Works for moths too!

Note that all of these moths are the same species! The 3 orange spots down the thorax indicate manduca rustica - the rustic sphinx moth, with a classic image shown at left. I've never caught any another species until last Sunday evening at 10:48, the 3rd moth to visit the blossom along the house. Shown at right it looked pretty similar, perhaps slightly smaller, though it had pink spots down its side! Submitting it for an ID request to Bug Guide, by morning I had an answer! Interestingly, it is called a pink-spotted hawk moth, or Agrius cingulate. I only captured the one image of it, but is the only non-rustic that I captured of 32 moth-visits over one and a half nights of imaging, and of course, over my previous sessions over the years. Rare for me, anyway!

Note that nearly all of these images were taken with a timer - I set it up to take images every 20 seconds on 30 August, and every 15 seconds on 2 September. It resulted in 1300+ images on the first night and 640 over about 3 hours the later. But the return of 32 moth visits was pretty good in my book (a little under 2%). As modern shooters are fond of saying - "digital film is cheap" - it isn't like we've got to pay for film and processing these days! Still, as a result, most of of the images are "accidental". Short of sitting in a chair and pushing the button manually or devising some sort of "moth detector", I can't see doing much better. I actually did have one come visit while I was checking the camera and caught 6 images over its 33 second visit by pushing the button myself. Shown at left in the montage, the number indicates the elapsed time in seconds after the first image. It shows that the moth made several "lunges" at the flower, presumably to reposition its proboscis and assist in feeding.

 I almost forgot!  On Sunday evening there was a full moon, and before heading to bed I tried to take one by the light of the full moon instead of the on-camera flash, like all the others. The result is at right - pretty good, thought the narrow depth of field tells you I opened up the aperture to its maximum 2.8 for the 30 second exposure.

As I've noticed before, the moths stop coming by about a half-hour before sunrise, and minutes later the bees arrive and do their thing till the flower closes an hour or so after sunrise. See the animated clip in the second paragraph to see for yourself. As I was taking a few close-ups before dawn, I shot the bee at left, shown at full camera resolution. Note the anthers, so packed with pollen early in the evening, are mostly bare here. Seen in drifts on some of the photos above, where did it end up? Well, at right is shown an 18 (!) frame focus stack of a cropped, extreme close-up of the stigma after a long night of pollinators. Besides the dark-looking straws (scales) from the moths, they are packed in spherical pollen grains, eventually to be seeds in the ripening fruit.

Anyway, the flowers and their pollinators are suitable distractions for observers looking for details! Give it a try - likely it will clear up eventually and show us some twinkly lights. But in the meantime - "gotta make some hay while the sun shines" - another Midwestern adage!


EDIT: I forgot to mention in this post that an earlier-in-the-summer blooming, only 3 months earlier hadn't brought ANY pollinators! At the end of May, a full night of camera monitoring showed nothing came by, not even the honeybees at the end of the night... Nothing sadder than an unused, unpollinated flower... Given the visitors we have this time of year, obviously the earlier blooming was before these pollinators were active in their life cycle...